Concept for slurry separation and biogas production

ABSTRACT

The present invention concerns an anaerobic digestion of animal manures, energy crops and similar organic substrates. The process is capable of refining nutrients comprised in the digested biomass to fertilizers of commercial quality. The invention also provides a method for oprocessing animal carcasses or fractions thereof including meat and bone meal etc., with the objective of providing an alternative means for processing the organic waste material of animal origin while at the same time facilitating the production of fertilizers. The risk of spreading BSE prions or any other prions to animals or humans is thus substantially reduced if not eliminated. The biogas and slurry separation system according to the present ivnention is preferably integrated with the operations of animal husbandries into a total concept in which the internal and external performances of animal husbandries are optimised. The internal performances concern quality aspects related to the management of the animal houses and include industrial hygiene, animal welfare, gaseous and dust emissions and food safety. The external performances concern mainly energy production and emissions to the environment of nutrients and greenhouse gases and the sale of high quality food product.

TECHNICAL FIELD OF THE INVENTION

[0001] In a first aspect, the present invention concerns an anaerobicdigestion of animal manures, energy crops and similar organicsubstrates. The process is capable of refining nutrients comprised inthe digested biomass to fertilizers of commercial quality. The biogasand slurry separation system according to the present invention ispreferably integrated with the operations of animal husbandries into atotal concept in which the internal and external performances of animalhusbandries are optimised.

[0002] One additional aspect of the invention is the possibleapplication for disposing off animal waste in the form of animalcarcasses, slaughterhouse waste, meat and bone meal, etc. The waste isrefined in the plant to fertilizers to be applied to agricultural land.A possible content of BSE-prions or other prions is substantiallyreduced if not eliminated in the whole process. The animal produce is inthis concept not used as fodder but fertilizer. The destruction ofpossible BSE prions in the biomass treated in the plant in combinationwith the use of the refined biomass as fertilizer in stead of foddersubstantially redices if not eliminates the risk of infecting animals orhumans with BSE-prions or modifications hereof.

[0003] The internal performances concern quality aspects related to themanagement of the animal houses and include industrial hygiene, animalwelfare, control of gaseous and dust emissions and food safety. Theexternal performances concern mainly energy production and control ofemissions to the environment of nutrients and greenhouse gasses and thesale of high quality food products as well as an alternative way fordisposing of animal carcasses and the like.

BACKGROUND OF THE INVENTION

[0004] Ammonia stripping

[0005] The chemistry of ammonia is well known and stripping of ammoniafrom different fluids is a well known industrial process. It has forexample been employed by the sugar industry (Bunert et al. 1995; Chacuket al. 1994; Benito and Cubero 1996) and by municipalities as treatmentof landfill reject (Cheung et al. 1997). Ammonia may also be strippedfrom pig slurry based on the same principles as in the industry (Liao etal. 1995).

[0006] The basic principle for large scale stripping of ammonia isincreasing pH and aerating and heating of the wastewater or the slurry.It is often Ca(OH)₂ or CaO which is used to increase pH. Other bases maybe employed such as NaOH or KOH. The lime, however, is used on anindustrial scale by for instance the cement industry and is thereforecheap and readily available as bulk ware.

[0007] Where the stripped ammonia is absorbed and an ammonia concentrateis produced sulphuric acid is often used in the absorption column.Sulphuric acid is an industrial bulk ware and is available in atechnical quality appropriate for use in absorption columns strippingammonia from slurry and other waste waters (e.g. Sacuk et al. 1994).

[0008] Based on the experience gained in the sugar industry it has beenfound that the most appropriate parameter values are: Temperature 70°C.; a pH in the range of about 10-12; and a liquid gas ration of 1:800,96% affectivity.

[0009] For stripping of ammonia from slurry it is found that the optimalparameter values at low temperature are: temperature 22° C.; pH of about10-12; liquid gas ratio of 1:2000, 90% affectivity, 150 h operation(Liao et al. 1995).

REFERENCES

[0010] Benito G. G. and Cubero M. T. G. (1996) Ammonia elimination frombeet sugar factory condensate streams by a stripping-reabsorbing system.Zuckerindustrie 121, 721-726.

[0011] Bunert U., Buczys R., Bruhns M., and Buchholz K. (1995) Ammoniastripping. Zuckerindustrie 120, 960-969.

[0012] Chacuk A., Zarzycki R., and Iciek J. (1994) A mathematical modelof absorption stripping columns for removal of ammonia from condensates.Zuckerindustrie 119, 1008-1015.

[0013] Cheung K. C., Chu L. M., and Wong M. H. (1997) Ammonia strippingas a pretreatment for landfill leachate. Water Air and Soil Pollution94, 209-221.

[0014] Liao, P. H., Chen A., and Lo K. V. (1995) Removal of nitrogenfrom swine manure wastewaters by ammonia stripping. Biotechnology &Applied Microbiology 54, 1720.

[0015] Alkali and Thermal Hydrolyses

[0016] Thermal pre-treatment of biomass before anaerobic digestion is atechnology which is well described in the literature, e.g. Li and Noike(1992). In resent years thermal pre-treatment of municipal waste hasalso been used on a commercial scale by Cambi AS, Billingstad, Norway.

[0017] Wang et al. (1997a and b) found that thermal pre-treatment ofmunicipal waste at 60° C. and a hydraulic residence time of 8 daysresulted in an increased methane production of 52.1%. A similar resultwas found by Tanaka et al. (1997), the combination however with alkalihydrolyses gave the highest increase in gas yield (200%). McCarty et al.have performed a series of studies showing that the combination ofthermal and alkali hydrolysis increases the gas yield substantially. ThepH however, shall be about 10 to 12, and preferably 11 or higher, beforethe chemical hydrolysis shall produce a significant additional gasyield.

[0018] The results of Wang et al. (1997) shows that the defaultparameter values for ammonia stripping under section 2.1 (the pH ofabout 10 to 12, preferably 11 or more, and the temperature of about 70°C. or more during a week) will increase the gas yield.

REFERENCES

[0019] Li Y. Y., and Noike T. (1992) Upgrading of anaerobic digestion ofwaste activated sludge by thermal pre-treatment. Water Science andTechnology 26, 3-4.

[0020] McCarty P. L., Young L. Y., Gossett J. M., Stuckey D. C., andHealy Jr. J. B. Heat treatment for increasing methane yield from organicmaterials. Stanford University, California 94305, USA.

[0021] Tanaka S., Kobayashi T. kamiyama K. and Bildan M. L. N. S. (1997)Effects of thermo chemical pre-treatment on the anaerobic digestion ofwaste activated sludge. Water Sdence and Technology 35, 209-215.

[0022] Wang Q., Noguchi C., Hara Y., Sharon C., Kakimoto K., and Kato Y.(1997a) Studies on anaerobic digestion mechanisms: Influence ofpre-treatment temperature on biodegradation of waste activated sludge.Environmental Technology 18, 999-1008.

[0023] Wang Q., Noguchi C. K:, Kuninobu M., Hara Y., Kakimoto K. OgawaH. I. And Kato Y. (1997b) Influence of hydraulic retention time onanaerobic digestion of pre-treated sludge. Biotechnology Techniques 11,105-108.

[0024] Sanitation

[0025] Sanitation of slurry before transporting and field applicationconstitute an important strategy for reducing the risk of spreading zoonoses and veterinary vira, bacteria and parasites (e.g. Bendixen 1999).Anaerobe digestion has proven effective in reducing the number of zoonoses in slurries but it does not eliminate these organisms (Bendixen1999; Pagilla et al. 2000). The use of CaO for sanitation of sewagesludge has also shown that Ascaris eggs and parasites (Eriksen et al.1996) and virus are reduced substantially but not completely (Turner andBurton 1997).

REFERENCES

[0026] Bendixen H. J. Hygienic safety—results of scientificinvestigations in Denmark (sanitation requirements in Danish biogasplants). Hohenheimer Seminar IEA Bioenergy Workshop March 1999.

[0027] Edksen L., Andreasen P. Ilsoe B. (1996) Inactivation of Ascarissuum eggs during storage in lime treated sewage sludge. Water Research30, 1026-1029.

[0028] Pagilla K. R., Kim H., and Cheunbam T. (2000) Aerobic thermopileand anaerobic mesopile treatment of swine waste. Water Research 34,2747-2753.

[0029] Turner C. and Burton C. H. (1997) The inactivation of viruses inpig slurries: a review. Bioresource Technology 61, 9-20.

[0030] Foam

[0031] Foam formation associated with anaerobic digestion may constitutea serious problem for operating the fermentors. A number of substancesfor remediation of foam are commercially available including differentpolymers, plant oils (e.g. rape oil) and different salts (e.g.Vardar-Sukan 1998). However, polymers may cause environmental concernsand are often expensive and ineffective.

REFERENCES

[0032] Vardar-Sukan F. (1998) Foaming: consequences, prevention anddestruction. Biotechnology Advances 16, 913-948.

[0033] Flocculation

[0034] Calcium-ions are a well known as means to flocculate substancesand particles due to the formation of calcium-bridges between organicand inorganic substances in solution or suspension thus forming “flocks”of particles (e.g. Sanin and Vesilind 1996). For this reason calcium hasbeen used for dewatering of sewage sludge (Higgins and Novak 1997).

REFERENCES

[0035] Higgins M. J. and Novak J. T. (1997). The effects of cat ions onthe settling and de-watering of activated sludge's: Laboratory results.Water Environment Research 69, 215-224.

[0036] Sanin F. D., and Vesilind P. A. (1996) Synthetic sludge: Aphysical/chemical model in understanding bio flocculation. WaterEnvironment Research 68, 927-933.

[0037] Decanter Centrifuge Slurry Separation, P Strpping

[0038] Decanter centrifuges have been applied to a number of industrialprocesses during the last 100 years.

[0039] Among recent examples of the use of decanter centrifuges is theNovo Nordisk plant in Kalundborg where all waste from the large insulinfermentation units is treated. Also municipal sludge is dewatered bymeans of decanter centrifuges (Alfa Laval A/S). The decanter centrifugesseparate the dry (solid) matter from the sludge or wastes, while thewater phase or the reject water is lead to a conventional sewagetreatment plant.

[0040] Experiments with separation of cattle, pig and degassed slurryshow firstly that decanter centrifuges can treat all manures without anydifficulties. It has also been found that the centrifuges removeapproximately 70% dry matter, 60-80% total P and only 14% of total Nfrom a slurry previously digested thermopile (Møller et al. 1999; Møller2000a). The corresponding values for raw slurry from cattle and pigswere somewhat lower. It should be noted that only 14% of total N isremoved from the waste.

[0041] The total treatment cost has been calculated to 5 Dkr. per m³slurry at a slurry volume of 20.000 tons or more. In those situationswhere the slurry volume exceeds 20.000 tons the decanter centrifuges arecost efficient and cheap instruments for separation of dry matter andtotal P from slurry (Møoller et al. 1999).

[0042] Under normal circumstances it is without any interest to treatslurry in a decanter centrifuge, because it is not associated with anyvolume reduction or other advantages to the farmers. The ammonia lossfollowing field application of treated slurry may be somewhat reduceddue to an increased infiltration rate into the soil (Møller 2000b), butthis is by far sufficient incentive to farmers for use of decantercentrifuges.

REFERENCES

[0043] Møller H. B. (2000a) Opkoncentrering af næringsstoffer ihusdyrgødning med dekantercentrifuge og skruepresse. Notat 12. September2000, Forskningscenter Bygholm.

[0044] Møller H. B. (2000b) Gode resultater med at separere gylle.Maskinbladet 25. august 2000.

[0045] Møller H. B., Lund I., and Sommer S. G. (1999) Solid-liquidseparation of livestock slurry: efficiency and cost.

[0046] Alfa Laval A/S Gylleseparering. Separeringsresultater meddecantercentrifuge.

[0047] P-Precipitation

[0048] Dissolved P is precipitated almost immediately following additionof Ca as calcium phosphate Ca₃(PO₄)₂ (Cheung et al. 1995).

REFERENCES

[0049] Cheung K. C., Chu L. M., and Wong M. H. (1997) Ammonia strippingas a pretreatment for landfill leachate. Water Air and Soil Pollution94, 209-221.

[0050] Prevention of Struvite Formation

[0051] It is an additional important aspect that the P precipitation incombination with the stripping of ammonia prevents the formation ofstruvite (MgNH₄PO₄). Struvite constitutes a significant working problemin heat-exchangers, transport in pipes, etc. (Krüger 1993). Themechanism is P-removal through formation of CaPO₄ as well as removal ofammonia through the stripping process. The P and ammonia removalprevents formation of struvite.

[0052] Krüger (1993) Struvit dannelse i biogasfeellesanlæg. KrügerWasteSystems AS.

[0053] Reject Water Filtration

[0054] Systems for final treatment and membrane filtration of rejectwater have been presented over the past 10 years in the form of e.g.membrane plants (BioScan A/S, Ansager ApS) and plants based on steamcompression (Funki A/S, Bjørnkjær Maskinfabrikker A/S). These systemsgenerally result in a gross cost per m³ slurry of 50-100 Dkr. The plantsare further not able to treat other types of manure but pig slurry.

[0055] The reduction of volume obtained by these plants is often notmore than 50-60%, meaning that field application of the remains in anycase depends on conventional devices. Hence, these plants are notcompetitive due to the cost level and/or a limited volume reduction.

[0056] However, it is important to consider and recognise the cost levelof these plants. It is also valuable to consider the energy use in theform electricity which the mechanical steam compression gives rise to,i.e. about 50 kWh per tons treated slurry. This means that membranes,under the assumption that the water phase to be filtered consists ofsalts and minimal amounts of dry matter only, which do not producescaling or fouling problems, may be able to out compete evaporationtechnologies.

REFERENCES

[0057] Argaman Y. (1984) Single sludge nitrogen removal in an oxidationditch. Water Research 18, 1493-1500.

[0058] Blouin M., Bisaillon J. G., Beudet R., and Ishague M. (1988)Aerobic biodegradation of organic matter of swine waste. BiologicalWastes 25, 127-139.

[0059] Bouhabila E. H., Aim R. B., and Buisson H. (1998) Microfiltration of activated sludge using submerged membrane with airbubbling (application to wastewater treatment). Desalination 118,315-322.

[0060] Burton C. H., Sneath R. W., Misselbrook T. H., and Pain B. F.(1998) Journal of Agricultural Engineering Research 71, 203.

[0061] Camarro L., Diaz J. M. and Romero F. (1996) Final treatments foranaerobically digested piggery effluents. Biomass and Bioenergy 11,483-489.

[0062] Doyle Y. and de la Noüe J. (1987) Aerobic treatment of swinemanure: Physicochemical aspects. Biological Wastes 22, 187-208.

[0063] Engelhardt N., Firk W., and Wamken W (1998) Integration ofmembrane filtration into the activated sludge process in municipalwastewater treatment. Water Science and Technology 38, 429-436.

[0064] Garraway J. L. (1982) Investigations on the aerobic treatment ofpig slurry. Agricultural Wastes 4,131-142.

[0065] Ginnivan M. J. (1983) The effect of aeration on odour and solidsof pig slurries. Agricultural Wastes 7,197-207.

[0066] Gönenc I. E. and Harremoës P. (1985) Nitrification in rotatingdisc systems-I. Criteria for transition from oxygen to ammonia ratelimitation. Water Research 19, 1119-1127.

[0067] Scott J. A.; Neilson D. J. Liu W., and Boon P. N. (1998) A dualfunction membrane bioreactor system for enhanced aerobic remediation ofhigh-strength industrial waste. Water Science and Technology 38,413-420.

[0068] Silva C. M., Reeve D. W., Husain H., Rabie H. R., and WoodhouseK. A. (2000) Journal of Membrane Science 173, 87-98.

[0069] Visvanathan C., Yang B-S., Muttamara S., and Maythanukhraw R.(1997) Application of air back flushing in membrane bioreactor. WaterScience and Technology 36, 259-266.

[0070] Zaloum R., Coron-Ramstrim A.-F. Gehr R. (1996) Finalclarification by integrated filtration within the activated sludgeaeration tank. Environmental Technology 17, 1007-1014.

[0071] Lime Cooking

[0072] A thermal and chemical hydrolysis at temperatures less than 100°C. and therefore pressures at about 1 atm represents one option forincreasing the availability of the organic matter for biogas generation.However, the complex carbohydrates such as cellulose, hemicelluloses andlignin is not completely hydrolysed by such treatments. Fibres fromstraw, maize and other crops are not made available for methaneformation by such treatments (Bjerre et al 1996; Schmidt and Thomsen1998; Thomsen and Schmidt 1999; Sirohi and Rai 1998). An alkali limecooking at moderate temperatures above 100° C. is well suited to renderthese substrates available to microbial decomposition (Curelli et al.1997; Chang et al. 1997; Chang et al. 1998).

[0073] This treatment, when applied to cellulose fibres from sugar canecut to 0.5 mm (with 4% CaO, 200° C. and 16 bar), disintegrates thecellulose to small organic acids as formic acid, acetic acid, lacticacid etc. The methane generation from treated cellulose is thus as highas 70% of the corresponding amount of carbohydrates as pure glucose(Azzam and Naser 1993). Also, green crops can be treated in a limecooker, but at lower temperatures. It has been shown that the optimalresult was achieved when water hyacinths were exposed to pH 11 and 121 °C. (Patel et al. 1993).

[0074] Formation of PAH and of substances inhibitory to methane bacteriamay be formed at elevated temperatures (Varhegyi et al. 1993; Patel etal. 1993). However, this phenomena has not been seen at the relativelymoderate temperatures used in lime cooking as compared the pyrolysis(Azzam et al. 1993). During pyrolysis the temperatures are so high thatthe biomass disintegrates directly to gasses as hydrogen, methane andcarbon monoxide but unfortunately also to PAH and other pollutants.

REFERENCES

[0075] Azzam A. M. and Nasr M. I. (1993) Physicothermochemicalpre-treatrnents of food processing waste for enhancing anaerobicdigestion and biogas fermentation. Journal of Environmental Science andEngineering 28,1629-1649.

[0076] Bjerre A. B., Olesen A. B., Fernquist T., Ploger A., Schmidt A.S. (1996) Pretreatment of wheat straw using combined wet oxidation andalkaline hydrolysis resulting in convertible cellulose andhemicelluloses. Biotechnology and Bioengineering 49, 568-577.

[0077] Chang V. S., Nagwani M., Holtzapple M. T. (1998) Originalarticles—Lime pretreatment of crop residues bagasse and wheat straw.Applied Biochemistry and Biotechnology Part A—Enzyme Engineering andBiotechnology 74, 135-160.

[0078] Chang V. S., Barry B., Holtzapple M. T. (1997) Lime pre-treatmentof switchgrass. Applied Biochemistry and Biotechnology Part A—EnzymeEngineering and Biotechnology 63-65, 3-20.

[0079] Curelli N., Fadda M. B., Rescigno A., Rinaldi A. C., soddu G.,Sollai E., Vaccargiu S.; Sanjust E., Rinaldi A. (1997) Mildalkaline/oxidative pretreatment of wheat straw. Process Biochemistry 32,665-670.

[0080] Patel V., Desai M., and Madamwar D. (1993) Thermo chemicalpre-treatment of water hyacinth for improved biomethanation. AppliedBiochemistry and Biotechnology 42, 67-74.

[0081] Schmidt A. S. and Thomsen A. B. (1998) Optimisation of wetoxidation pretreatment of wheat straw. Bioresource Technology 64,139-152.

[0082] Sirohi S. K. and Rai S. N. (1998) Optimisation of treatmentconditions of wheat straw with lime: Effect of concentration, moisturecontent and treatment time on chemical composition and in vitrodigestibility. Animal Feed Science and Technology 74, 57-62.

[0083] Thomsen A. B. and Schmidt A. S. (1999) Further development ofchemical and biological processes for production of bio ethanol:optimisation of pre-treatment processes and characterisation ofproducts. Rise National Laboratory, Roskilde, Denmark.

[0084] Varhegyi G., Szabo P., Mok W. S. L., and Antal M. J. (1993)Kinetics of the thermal decomposition of cellulose in sealed vessels atelevated pressures. Journal of Analytical and Applied Pyrolysis 26,159-174.

[0085] Energy Crop Silage

[0086] The conventional use of energy crops is mainly in the form ofsolid fuel for burning (willow as wood chops, straw or whole seed) or asfuel for engines (rape oil). On an experimental basis beets and straw isused for production of ethanol (Parsby; Sims 2001; Gustavsson et al.1995; Wyman and Goodman 1993; Kuch 1998). In other parts of the worldthe use of energy crops is widespread and subject to much research. Theuse of terrestrial as well as marine and freshwater plants is welldocumented (Gunaseelan 1997; Jewell et al. 1993; Jarwis et al 1997).Some studies would appear to indicate that anaerobic fermentation ofenergy crops is competitive to other uses of biomass (Chynoweth D. P.,Owens J. M., and Legrand R. 2001).

[0087] The use of energy crops is well motivated. The use of straw isorganised in a way which probably makes this practise a concept to beseen for a number of years to come. The use of wood chops seems to beeconomical and practical viable. Incineration of grain cereals on theother hand has given rise to ethical objections. The production of graincereals is also inevitable associated with the use of fertilizers andpesticides and N-losses from the fields. N is also lost during theburning of the biomass.

REFERENCES

[0088] Beck J. Co-fermentation of liquid manure and beets as aregenerative energy. University of Hohenheim, Dep. AgriculturalEngineering and Animal Production. Personal communication.

[0089] Chynoweth D. P., Owens J. M., and Legrand R. (2001) Renewablemethane from anaerobic digestion of biomass. Renewable Energy 22, 1-8.

[0090] Gunaseelan V. N. (1997) Anaerobic digestion of biomass formethane production: A review. Biomass and Bioenergy 13, 83-114.

[0091] Gustavsson L, Borjesson P., Bengt J., Svenningsson P. (1995)Reducing CO₂ emissions by substituting biomass for fossil fuels. Energy20, 1097-1113.

[0092] Jewell W. J., Cummings R. J., and Richards B. K. (1993) Methanefermentation of energy crops: maximum conversion kinetics and in situbiogas purification. Biomass and Bioenergy 5, 261-278.

[0093] Jarvis Å., Nordberg Å., Jarlsvik T., Mathiesen B., and SvenssonB. H. (1997) Improvement of a grass-clover silage-fed biogas process bythe addition of cobalt. Biomass and Bioenergy 12, 453-460.

[0094] Kuch P. J., Crosswhite W. M. (1998) The agricultural regulatoryframework and biomass production. Biomass and Bioenergy 14, 333-339.

[0095] Parsby M. Halm og energiafgrøder—analyser af økonomi, energi ogmiljø. Rapport Nr. 87, Statens Jordbrugs og Fiskeriøkonomiske Institut.

[0096] Sims R. H. E. (2001) Bioenergy—a renewable carbon sink. RenewableEnergy 22, 31-37.

[0097] Wyman C. E. and Goodman B. J. (1993) Biotechnology for productionof fuels chemicals and materials from biomass. Applied Biochemistry andBiotechnology 39, 41-59.

[0098] Banks C. J. and Humphreys P. N. (1998) The anaerobic treatment ofa lignocellulosic substrate offering little natural pH bufferingcapacity. Water Science and Technology 38, 29-35;

[0099] Colleran E., Wilkie A., Barry M., Faherty G., O'kelly N. andReynolds P. J. (1983) One and two stage anaerobic filter digestion ofagricultural wastes. Third Int Symp. on Anaerobic Digestion, pp.285-312, Boston Mass. (1983).

[0100] Dugba P. N., and Zhang R. (1999) Treatment of dairy wastewaterwith two-stage anaerobic sequencing batch reactor systems—thermopileversus mesopile operatons. Bioresource Technology 68, 225-233.

[0101] Ghosh S., Ombregt J. P., and Pipyn P. (1985) Methane productionfrom industrial wastes by two-phase digestion. Water Research 19,1083-1088.

[0102] Han Y., Sung S., and Dague R. R. (1997) Temperature-phasedanaerobic digestion of wastewater sludge's. Water Science and Technology36, 367-374.

[0103] Krylova N. I., Khabiboulline R. E., Naumova R. P. Nagel M. A.(1997) The influence of ammonium and methods for removal during theanaerobic treatment of poultry manure. Journal of Chemical Technologyand Biotechnology 70, 99-105.

[0104] Hansen K. H., Angelidaki I., Ahring B. K. (1998) Anaerobicdigestion of swine manure: inhibition by ammonia. Water Research 32,5-12.

[0105] Kayhanian M. (1994) Performance of high-solids anaerobicdigestion process under various ammonia concentrations. Journal ofChemical Technology and Biotechnology 59, 349-352.

[0106] Wang Q., Noguchi C. K., Kuninobu M., Hara Y., Kakimoto K., OgawaH. I., and Kato Y. (1997) Influence of hydraulic retention time onanaerobic digestion of pre-treated sludge. Biotechnology Techniques 11,105-108.

[0107] Disposal Systems for Animal Cadavers etc.

[0108] The present disposal system for animal cadavers is organised byregistrating plants which are licensed to process the animal cadavers.The cadavers are primarily used for production of meat and bone mealwhich traditionally have been used for annimal foodstuff.

[0109] The present BSE-crisis have stopped this practise by a regulatoryorder from the EU-commission, stating that meat and bone meal cannot beused as animal foodstuff.

[0110] The livestock sector and associated buisnesses in Europe thusface the challenge to find alternative use of meat and bone meal oralternative ways of disposing off the meal. However, this is a difficulttask because of the constraints imposed by the risk of spreding BSEprions or other prions possibly present in the meal or other fractionsof animal cadavers. The use of meat and bone meal or animal cadavers inconventional biogas plants is certainly not advisable and only partlypossible. The processing of animal caderves in plants licensed toprocess such animals is useually performed at temperatures around 130°C., with pressure around 2-3 bar with a retention time of 20 min. Suchconditions are not to be found in conventional biogas plants.

[0111] The below mentioned patents and patent applications form part ofthe prior art.

[0112] DE3737747 describes a plant and a process to stripping of N. CaOis added to the manure by which the ammonia is stripped, said ammonia isabsorbed in a water solution containing hydrocloric acid. A number ofaspects of the invention are not described by this reference. Thisapplies, among other things, to the pre-treatment such as the alkalinehydrolysis, welfare in the animal houses, utilization of energi crops,absorbing of ammonia in a sulfur solution, the precipitation of P,prevention of struvite formation etc. and the use of biogas through alocal gas engine or through an established pipeline for natural gas.

[0113] DE4201166 describes a method of concurrent treatment of differentorganic waste products, in which the waste products are separated intothree fractions containing different amounts of solid components. Solidfractions are homogenised before fermentation and biogas production. Anumber of aspects of the invention are not described by this reference.This applies, among other things, to the pre-treatment such as thealkaline hydrolysis, welfare in the animal houses, utilization of energicrops, absorbing of ammonia in a sulfur solution, the precipitation ofP, prevention of struvite formation etc. and the use of biogas through alocal gas engine or through an established pipeline for natural gas.

[0114] DE4444032 describes a plant and a process in which slurry i thefirst reactor is stirred, aerated and added lime to pH 9.5 to stripammonia. In the second reactor a salt containing ferro and a polymer areadded to neutralise the slurry and precipitate solids. A number ofaspects of the invention are not described by this reference. Thisapplies, among other things, to the pre-treatment such as the alkalinehydrolysis, welfare in the animal houses, utilization of energi crops,absorbing of ammonia in a sulfur solution, the precipitation of P,prevention of struvite formation etc. and the use of biogas through alocal gas engine or through an established pipeline for natural gas.

[0115] DE196615063 describes a process in which ammonia is stripped fromfermented manure. A number of aspects of the invention are not describedby this reference. This applies, among other things, to thepre-treatment such as the alkaline hydrolysis, utilization of energicrops, the precipitation of P, prevention of struvite formation etc. andthe use of biogas through a local gas engine or through an establishedpipeline for natural gas.

[0116] EP0286115 describes a method to production of biogas in whichmanure is added fat acids or compositions containing fat acids. A numberof aspects of the invention are not described by this reference. Thisapplies, among other things, to the pretreatment such as the alkalinehydrolysis, utilization of energi crops, the precipitation of P,prevention of struvite formation etc. and the use of biogas through alocal gas engine or through an established pipeline for natural gas.

[0117] EP0351922 describes a plant and a process in which the strippingof ammonia, carbon dioxide and phosphat occurs from liquid manure. Themanure is transported from the farm by tank cars to the plant where theslurry is treated with hot air and by that partly stripped of ammoniaand carbon dioxide. The remaining part of the slurry is heated and limeis added to pH 10-11, by which more ammonia is stripped and calciumphosphate is formed. The stripped ammonia is absorbed in an acidicsolution by the formation of ammonium salt, which is dried and utilizedas fertilizers. A decanter centrifuge is used to separate solid partsfrom the slurry. A number of aspects of the invention are not describedby this reference. This applies, among other things, to thepre-treatment such as the alkaline hydrolysis, welfare in the animalhouses, utilization of energi crops, prevention of struvite formationetc. and the use of biogas through a local gas engine or through anestablished pipeline for natural gas.

[0118] ES2100123 describes a plant and a process in which liquid manureis cleaned. Organic components is degraded and precipitated solids isremoved by decanter centrifugation. The liquid is added acid and isspread in the land or is further cleaned by aeration and by thatstripping of ammonia. The cleaned liquid is diverted to a waterpurifying plant. A number of aspects of the invention are not describedby this reference. This applies, among other things, to thepre-treatment such as the alkaline hydrolysis, welfare in the animalhouses, stripping of ammonia at an early step, ublizabon of energicrops, prevention of struvite formation etc. and the use of biogasthrough a local gas engine or through an established pipeline fornatural gas.

[0119] FR2576741 describes a process to the production of biogas byfermenting of liquid manure. The slurry is treated with lime andprecipitated components is removed. A number of aspects of the inventionare not described by this reference. This applies, among other things,to the pretreatment such as the alkaline hydrolysis, utilization ofenergi crops, the precipitation of P, prevention of struvite formationetc. and the use of biogas through a local gas engine or through anestablished pipeline for natural gas.

[0120] GB 2013170 describes a plant and a method to production ofbiogas. In the first reactor the organic material is acidified and thesolid fraction is removed. The liquid fraction is diverted to the secondreactor in which an anaerobic degradation occurs with the production ofmethane gas. A number of aspects of the invention are not described bythis reference. This applies, among other things, to the pre-treatmentsuch as the alkaline hydrolysis, welfare in the animal houses, strippingof ammonia, utilization of energi crops, prevention of struviteformation etc. and the use of biogas through a local gas engine orthrough an established pipeline for natural gas.

[0121] DE19644613 describes a method to produce solid fertilisers frommanure. The liquid manure is added substrate from the biogas productiontogether with CaO or Ca(OH)₂. The stripped ammonia is collected. Anumber of aspects of the invention are not described by this reference.This applies, among other things, to the pretreatment such as thealkaline hydrolysis, utilization of energi crops, the precipitation ofP, prevention of struvite formation etc. and the use of biogas through alocal gas engine or through an established pipeline for natural gas.

[0122] DE19828889 describes co-fermentation of harvested crops andorganic waste with the production of biogas. The material is homogenisedand fermented. A number of aspects of the invention are not described bythis reference. This applies, among other things, to the pre-treatmentsuch as the alkaline hydrolysis, utilization of energi crops, theprecipitation of P, prevention of struvite formation etc. and the use ofbiogas through a local gas engine or through an established pipeline fornatural gas.

[0123] U.S. Pat. No. 4,041,182 describes a method to production ofanimal foodstuff from organic waste. A number of aspects of theinvention are not described by this reference. This applies, among otherthings, to the pre-treatment such as the alkaline hydrolysis,utilization of energi crops, the precipitation of P, prevention ofstruvite formation etc. and the use of biogas through a local gas engineor through an established pipeline for natural gas.

[0124] U.S. Pat. No. 4,100,023 describes a plant and a process to theproduction of methane gas and fertilisers. In the first reactor an aerobdegradation of the homogenised material is performed. In the secondreactor which is heated, an anaerob degradation and the biogasproduction occurs. Fertilisers are produced as liquids. A number ofaspects of the invention are not described by this reference. Thisapplies, among other things, to the pre-treatment such as the alkalinehydrolysis, welfare in the animal houses, stripping of ammonia,utilization of energi crops, prevention of struvite formation etc. andthe use of biogas through a local gas engine or through an establishedpipeline for natural gas.

[0125] U.S. Pat. No. 4,329,428 describes a plant for anaerobicdecomposition, in particular material from various green plants, and theuse of the produced biogas. The plant is based on the decomposition andcaused by mesofilic or thermopile anaerobic bacteria. A number ofaspects of the invention are not described by this reference. Thisapplies, among other things, to the pre-treatment such as the alkalinehydrolysis, the stripping of ammonia, the precipitation of P, preventionof struvite formation etc. and the use of biogas through a local gasengine or through an established pipeline for natural gas.

[0126] U.S. Pat. No. 4,579,654 describes a plant and a process toproduce biogas from organic materials. Solid materials are hydrolysed,acidified and fermented. A number of aspects of the invention are notdescribed by this reference. This applies, among other things, to thepre-treatment such as the alkaline hydrolysis, welfare in the animalhouses, stripping of ammonia, utilization of energi crops, prevention ofstruvite for O mation etc. and the use of biogas through a local gasengine or through an established pipeline for natural gas.

[0127] U.S. Pat. No. 4,668,250 describes a process in which ammonia isremoved from the liquid fraction by aeration. A number of aspects of theinvention are not described by this reference. This applies, among otherthings, to the pre-treatment such as the alkaline hydrolysis,utilization of energi crops, the precipitation of P, prevention ofstruvite formation etc. and the use of biogas through a local gas engineor through an established pipeline for natural gas.

[0128] U.S. Pat. No. 4,750,454 describes a plant for anaerobic digestionof animal manure and the use of the biogas produced by the process. Theplant is based on decomposition caused by mesofilic or thermopileanaerobic bacteria and utilizes a local gas powdered engine equippedwith a generator. A number of aspects of the invention are not describedby this reference. This applies, among other things, to the pretreatmentsuch as the alkaline hydrolysis, the stripping of ammonia, theprecipitation of P, prevention of struvite formation etc. and the use ofbiogas through a local gas engine or through an established pipeline fornatural gas.

[0129] U.S. Pat. No. 5,071,559 describes a method to treatment ofmanure. The manure is added water and the mixture is acidified. Liquidis removed by steamproduction, which again is condensated in anotherreactor and treated anaerobic to produce biogas. The fermented liquid isfraction is then treated by an aerob process. A number of aspects of theinvention are not described by this reference. This applies, among otherthings, to the pre-treatment such as the alkaline hydrolysis, welfare inthe animal houses, stripping of ammonia, utilization of energi crops,prevention of struvite formation etc. and the use of biogas through alocal gas engine or through an established pipeline for natural gas.

[0130] U.S. Pat. No. 5,296,147 describes a process to treat manure andother organic components. The organic waste fermentes and is thennitrified and further denitrified. A number of aspects of the inventionare not described by this reference. This applies, among other things,to the pre-treatment such as the alkaline hydrolysis, welfare in theanimal houses, stripping of ammonia, utilization of energi crops,prevention of struvite formation etc. and the use of biogas through alocal gas engine or through an established pipeline for natural gas.

[0131] U.S. Pat. No. 5,389,258 describes a method to production ofbiogas from semi-solid and solid organic waste. A number of aspects ofthe invention are not described by this reference. This applies, amongother things, to the pre-treatment such as the alkaline hydrolysis,welfare in the animal houses, stripping of ammonia, utilization ofenergi crops, prevention of struvite formation etc. and the use ofbiogas through a local gas engine or through an established pipeline fornatural gas.

[0132] U.S. Pat. No. 5,494,587 describes a process with a catalytictreatment of manure including reduction of the nitrogen concentration. Anumber of aspects of the invention are not described by this reference.This applies, among other things, to the pre-treatment such as thealkaline hydrolysis, welfare in the animal houses, stripping of ammonia,utilization of energi crops, prevention of struvite formation etc. andthe use of biogas through a local gas engine or through an establishedpipeline for natural gas.

[0133] U.S. Pat. No. 5,525,229 describes a general procedure foranaerobic digestion of organic substrates under thermopile as well asmesofilic conditions.

[0134] U.S. Pat. No. 5,593,590 describes separation and treatment ofliquid and solid organic waste following a separation of the twofractions. The liquid fraction is fermented with the production ofbiogas followed by removing of precipitated solid components, whichpartly is recirculated in the process. The solid fraction is treated inan aerob process and is produced into compost, fertilisers or animalfoodstuff. Part of the produced biogas comprising methane and CO₂ isreuse to the reduction of the pH level in the liquid fraction by a CO₂absorbtion. Solids is precipitated from liquid fractions e.g. by adecanter centrifuge, and ammonia is stripped from the liquid by a pH of9-10. Reject water can be used to clean stables. A number of aspects ofthe invention are not described by this reference. This applies, amongother things, to the pretreatment such as the alkaline hydrolysis,welfare in the animal houses by use of straw, stripping of ammoniabefore biogas production, utilizabon of energi crops, prevention ofstruvite formation etc. and the use of biogas through a local gas engineor through an established pipeline for natural gas.

[0135] U.S. Pat. No. 5,616,163 describes a method to treatment of manureby which nitrogen is utilised in the production of fertilisers. Liquidmanure is added CO2 and/or CaSO4 by which ammonia is stripped. A numberof aspects of the invention are not described by this reference. Thisapplies, among other things, to the pre-treatment such as the alkalinehydrolysis, welfare in the animal houses by use of straw, stripping ofammonia before biogas production, utilization of energi crops,prevention of struvite formation etc. and the use of biogas through alocal gas engine or through an established pipeline for natural gas.

[0136] U.S. Pat. No. 5,656,059 describes a method to treat manure bywhich nitrogen is utilised in the production of fertilisers more or lessby nitrification. A number of aspects of the invention are not describedby this reference. This applies, among other things, to thepre-treatment such as the alkaline hydrolysis, welfare in the animalhouses by use of straw, stripping of ammonia before biogas production,utilization of energi crops, prevention of struvite formation etc. andthe use of biogas through a local gas engine or through an establishedpipeline for natural gas.

[0137] U.S. Pat. No. 5,670,047 describes a general procedure foranaerobic decomposition of organic substrates to gases.

[0138] U.S. Pat. No. 5,681,481 U.S. Pat. No. 5,783,073 and U.S. Pat. No.5,851,404 describes a process and an apparatus to stabilising of slurry.Lime is added to pH≧12 and the mass is heated to at least 50.degree.Cfor 12 hours. Ammonia is stripped, and is either discharged into theatmosphere or recirculated in the system. A ‘preheat chamber’ can beused as well as decanter centrifugation as well as mixing of the sludgeto keep it in a liquid condition. The sludge is spread to land. A numberof aspects of the invention are not described by this reference. Thisapplies, among other things, to the pre-treatment such as the alkalinehydrolysis, welfare in the animal houses by use of straw, stripping ofammonia before biogas production, utilization of energi crops,prevention of struvite formation etc. and the use of biogas through alocal gas engine or through an established pipeline for natural gas.

[0139] U.S. Pat. No. 5,746,919 describes a process in which organicwaste is treated in a thermofil anaerob reactor followed by treatment ina mesofil anaerob reactor. In both reactors a production of methane gasoccurs. A number of aspects of the invention are not described by thisreference. This applies, among other things, to the pre-treatment suchas the alkaline hydrolysis, welfare in the animal houses by use ofstraw, stripping of ammonia before biogas production, utilization ofenergi crops, prevention of struvite formation etc. and the use ofbiogas through a local gas engine or through an established pipeline fornatural gas.

[0140] U.S. Pat. No. 5,773,526 describes a process in which liquid andsolid organic waste is fermented first by a mesofil process and therebyby a thermofil process. Solid components is hydrolysed and acidifies. Anumber of aspects of the invention are not described by this reference.This applies, among other things, to the pre-treatment such as thealkaline hydrolysis, welfare in the animal houses by use of straw,stripping of ammonia before biogas production, utilization of energicrops, prevention of struvite formation etc. and the use of biogasthrough a local gas engine or through an established pipeline fornatural gas.

[0141] U.S. Pat. No. 5,782,950 describes fermentation of biologicalwaste by a homogenisation, aeration and heating of the mass. The wasteis fractionated into a liquid and a solid fraction. The solids isproduced into compost. The liquids is fermented by anaerob mesofil andthermofil process with production of biogas. Reject water isrecirculated from the biogas reactor to the homogenisation process.Reject water from the biogas reactor is treated in a plant clarificationinstallation. A number of aspects of the invention are not described bythis reference. This applies, among other things, to the pre-treatmentsuch as the alkaline hydrolysis, welfare in the animal houses, strippingof ammonia before biogas production, utilization of energi crops,prevention of struvite formation etc. and the use of biogas through alocal gas engine or through an established pipeline for natural gas.

[0142] U.S. Pat. No. 5,853,450 describes a method to procude pasteurisedcompost from organic waste and green plant materials. The pH of theorganic is increased to 12 and heated to above 55.degree.C. When thegreen plant material is added pH is lowered to 7-9.5. The mixture isfermented. A number of aspects of the invention are not described bythis reference. This applies, among other things, to the pre-treatmentsuch as the alkaline hydrolysis, welfare in the animal houses, strippingof ammonia before biogas production, prevention of struvite formationetc. and the use of biogas through a local gas engine or through anestablished pipeline for natural gas. U.S. Pat. No. 5,863,434 describesa method to stabilise organic waste by degradation in a psychrofilanaerob process. A number of aspects of the invention are not describedby this reference. This applies, among other things, to thepre-treatment such as the alkaline hydrolysis, welfare in the animalhouses, stripping of ammonia before biogas production, prevention ofstruvite formation etc. and the use of biogas through a local gas engineor through an established pipeline for natural gas.

[0143] U.S. Pat. No. 6,071,418 describes a method and a stystem to treatmanure with ozon in a way that induces an aerob and an anaerob zonewithin the material. A number of aspects of the invention are notdescribed by this reference. This applies, among other things, to thepre-treatment such as the alkaline hydrolysis, welfare in the animalhouses, stripping of ammonia before biogas production, prevention ofstruvite formation etc. and the use of biogas through a local gas engineor through an established pipeline for natural gas.

[0144] U.S. Pat. No. 6,171,499 describes an improved method tofermentate domestic and industrial waste. The waste is anaerob digestedwith production of biogas, which is utilized in a gas turbine incombination with natural gas. The fermented material is dehydrated andthe sludge is diverted to a incineration plant A number of aspects ofthe invention are not described by this reference. This applies, amongother things, to the pretreatment such as the alkaline hydrolysis,welfare in the animal houses, stripping of ammonia before biogasproduction, prevention of struvite formation etc. and the use of biogasthrough a local gas engine or through an established pipeline fornatural gas.

[0145] WO8400038 describes the production of biogas and degassed andstabilised fertilisers. The thermofil degradation occurs in an innerreactor and the mesofil degradation in an outer reactor. A number ofaspects of the invention are not described by this reference. Thisapplies, among other things, to the pre-treatnent such as the alkalinehydrolysis, welfare in the animal houses, stripping of ammonia beforebiogas production, prevention of struvite formation etc. and the use ofbiogas through a local gas engine or through an established pipeline fornatural gas.

[0146] WO8900548 describes the utilization of Ca-ions and Mg-ions in thebiogas production. The metal ions inhibit foam production. A number ofaspects of the invention are not described by this reference. Thisapplies, among other things, to the pretreatment such as the alkalinehydrolysis, welfare in the animal houses, stripping of ammonia beforebiogas production, prevention of struvite formation etc. and the use ofbiogas through a local gas engine or through an established pipeline fornatural gas.

[0147] WO9102582 describes a plant and a method to produce gas and avoidspreading of harmfull compounds to the surroundings by washing the gas.A number of aspects of the invention are not described by thisreference. This applies, among other things, to the pre-treatment suchas the alkaline hydrolysis, welfare in the animal houses, stripping ofammonia before biogas production, prevention of struvite formation etc.and the use of biogas through a local gas engine or through anestablished pipeline for natural gas.

[0148] WO9942423 describes a method and a plant to the production ofbiogas. Fibres and particles from manure is composted and the liquidfraction is fermented anaerobically, stripped for nitrogen. The salts ofP and K is utilised for fertilisers by reverse osmosis. A number ofaspects of the invention are not described by this reference. Thisapplies, among other things, to the pre-treatment such as the alkalinehydrolysis, welfare in the animal houses, stripping of ammonia beforebiogas production, prevention of struvite formation etc. and the use ofbiogas through a local gas engine or through an established pipeline fornatural gas.

[0149] www.igb.fhg.de/Uwbio/en/Manure.en.html describes a process toproduce biogas from manure. From degassed manure the solid fraction isused to produce compost. From the liquid fraction is nitrogen collectedand is used as fertilisers. A decanter cetntifuge can be used toseparate solid components from the mixture. A number of aspects of theinvention are not described by this reference. This applies, among otherthings, to the pre-treatment such as the alkaline hydrolysis, welfare inthe animal houses, stripping of ammonia before biogas production,prevention of struvite formation etc. and the use of biogas through alocal gas engine or through an established pipeline for natural gas.http://riera.ceeeta.pt/images/ukbio_mass.htm describes a production ofbiogas by anaerob degradation. A decanter centrifuge can be used in thesystem. A number of aspects of the invention are not described by thisreference. This applies, among other things, to the pre-treatment suchas the alkaline hydrolysis, welfare in the animal houses, stripping ofammonia before biogas production, prevention of struvite formation etc.and the use of biogas through a local gas engine or through anestablished pipeline for natural gas.

[0150] www.biogas.ch/f+e/memen.htm describes possibilities to reduce amixture from solid components. Rotating disc reactor, fixed filmreactor, ultrafiltration and reverse osmose is mentioned. A number ofaspects of the invention are not described by this reference. Thisapplies, among other things, to the pre-treatment such as the alkalinehydrolysis, welfare in the animal houses, stripping of ammonia beforebiogas production, prevention of struvite formation etc. and the use ofbiogas through a local gas engine or through an established pipeline fornatural gas.

[0151] www.biogas.ch(f+e/grasbasi.htm describes anaerob degradation ofsilage energi crops and manure with the production of biogas. Twoprocesses is described: 1. Silage energi crops is cut into 1-3 cm anddirected to a liquid fraction containing the manure. The mixture ifermented at 35° C. 2. A dry fermentation of manure and silage energycrops without adding further liquid. A number of aspects of theinvention are not described by this reference. This applies, among otherthings, to the pretreatment such as the alkaline hydrolysis, welfare inthe animal houses, stripping of ammonia before biogas production,prevention of struvite formation etc. and the use of biogas through alocal gas engine or through an established pipeline for natural gas.

[0152] www.biogas.ch/f+e/2stede.htm describes the production of biogas.The organic waste is hydrolysed and acidified in a rotating sieve-drumfrom which the liquid fraction continous is directed to anaerobdegradation of with the production of biogas. A number of aspects of theinvention are not described by this reference. This applies, among otherthings, to the pre-treatment such as the alkaline hydrolysis, welfare inthe animal houses, stripping of ammonia before biogas production,prevention of stuvite formation etc. and the use of biogas through alocal gas engine or through an established pipeline for natural gas.

SUMMARY OF THE INVENTION

[0153] The present invention shall demonstrate a new way of utilizingenergy crops, namely through anaerobic co-digestion in farm scale biogasplants with animal manures. The process also includes slurry separation,i.e., refinement of nutrients in the animal manures.

[0154] The invention can also be used to co-digest animal cadavers, meatand bone meal etc. with animal manures/energy crops and thus to providea way of disposing off animal cadavers etc. while at the same timefacilitate the production of fertilizers produced from the input of theanimal wastes along with the crops, manures etc.

[0155] The process design makes it possible to use annual fodder cropssuch as beets, maize or clover grass, all crops with a higher dry matteryield per hectare than grain cereals. The fodder crops are alsobeneficial as “green crops” and in crop rotations. The energy potentialwhen using the set aside land for energy crop production shall thus bedemonstrated by the present concept.

[0156] The central and obvious vision—under a wide variety ofcircumstances—is that the biogas production based on this concept shallin the future be competitive compared to the use of natural gas and thusbe commercial attractive and preferably not subsidised. It is also thevision that the energy production shall constitute a substantial part ofthe Danish energy consumption, i.e. of the same order of magnitude ofthe use of natural gas (about 150 PJ annually). In addition to thiseffect are the benefits in terms of environment, animal welfare and foodsafety.

[0157] Parsby has estimated an energy potential when using energy crops,in particular grain cereals, to 50-80 PJ annually. In the short run thisrequires an area of 150.000 ha and in the longer run an area of 300.000ha. However, based on an dry matter yield of 15 tons per ha in beetsincluding tops to be digested in biogas plants the energy potentialbecomes about 100 PJ annually. The energy from the co-digested manuresshall be added to this (about 25 PJ). With the new cultivars of beetsthe yields of dry matter may substantially exceed the present levels,i.e., yields of the order of 25 tons per hectare.

[0158] The core of the invention is a combination of processes whichallows increased biogas production, stripping of ammonia and asubsequent optional further use and processing of the digested andstripped remains (the reject water).

[0159] It is characteristic that the core of the invention allowsfurther simple and robust processes to be integrated with the core ofthe invention. A simple and robust energy plant with outstanding energyand economic performances as compared to conventional plants isachieved. The energy plant is further integrated with the management ofthe animal holdings and the agricultural land. Hence a number of aspectsconstitute the invention.

[0160] In a first preferred aspect the invention may be applied tocombat infections and spread of animal microbial and parasitic pathogenssuch as Campylobacter, Salmonella, Yersinia, Acaris and similarmicrobial and parasitic organisms to air and agricultural land. Thethreat to humans of being infected is thus reduced if not eliminated.

[0161] In a second preferred aspect the invention may be applied toreduce BSE prions contained in manures, fodder, slaughterhouse waste,flesh and bone meal etc. This is achieved by a combination ofpre-treatment and digestion. As part of this aspect, the presentinvention provides one possibility for handling animal cadavers,slaughter house waste etc. which enables the exploitation of thenutrients contained in the animal cadavers as fertilizers. The reductionand/or elimination of BSE prions contained in animal cadavers, meat andbone meal etc. but also manures, fodder, slaughterhouse waste, etc.during the process of the invention is a prerequisite for this way ofhandling the waste This is achieved according to the invention by acombination of pre-treatment and digestion. This procedure is analternative to the present proceedure (however now presently prohibitedby the EU commission) of processing animal carcasses in central plantsand producing various products such as meat and bone meal to be usedmainly as animal feed.

[0162] In a third preferred aspect the invention may be applied toseparate the main nutrients nitrogen (N) and phosphorus (P) from animalmanures and refine the nutrients to fertilizer products of commercialquality.

[0163] In a fourth preferred aspect the invention may be applied toproduce large amounts of biogas from a wide range of organic substratesincluding all types of animal manures, energy crops, crops residues andother organic wastes.

[0164] In a fifth preferred aspect the invention may be applied toensure optimal animal welfare and health when stabled in the animalhouses while at the same time reducing emissions of dust and gasses suchas ammonia. This is achieved by flushing or re-circulating reject waterthrough the animal houses.

[0165] In a sixth preferred aspect the invention may be applied tobenefit from the full range of advantages associated with the variousaspects of the invention.

[0166] In further preferred aspects any combination of the coreinvention with any one or more of the other aspects mentioned may bepreferred.

BRIEF DESCRIPTION OF THE FIGURES

[0167]FIG. 1 discloses one preferred embodiment of the presentinvention. In this embodiment, manure, preferably in the form of aslurry, generated in a house or stable (1) for the rearing of animals,including domestic animals, such as pigs, cattle, horses, goats, sheep;and/or poultry, including chickens, turkeys, ducks, geese, and the like,is transferred to either one or both of a first pretreatment tank (2)and/or a second pretreatment tank (3).

[0168] The working principles are that the manure, preferably in theform of a slurry including, in one embodiment, water such as rejectwater used for cleaning the house or stable, is diverted to the firstpretreatment tank comprising a stripper tank, where ammonia is strippedby means of addition to the stripper tank of e.g. CaO and/or Ca(OH)₂.However, additlon of CaO and/or Ca(OH)₂ to the slurry may also takeplace prior to the entry of the slurry into the first treatment tank orstripper tank.

[0169] At the same time as the addition of CaO and/or Ca(OH)₂, or at alater stage, the pretreatment tank comprising the stripper tank issubjected to stripping and/or heating, and the stripped N or ammonia ispreferably absorbed prior to being stored in a separate tank (11). Thestripped N including ammonia is preferably absorbed to a column in thestripper tank comprised in the first treatment tank before beingdirected to the separate tank for storage.

[0170] Organic materials difficult to digest by microbial organismsduring anaerobic fermentation are preferably pretreated in a secondpretreatment tank (3) prior to being directed to the first pretreatmenttank (2) comprising the stripper tank as described herein above. Suchorganic materials typically comprise a significant amounts of e.g.cellulose and/or hemicellulose and/or lignin, e.g. preferably more than50% (w/w) cellulose and/or hemicellulose and/or lignin per dry weightorganic material, such as straws, crops, including corn, crop wastes,and other solid, organic materials. N including ammonia is subsequentlystripped from the pretreated organic material.

[0171] In both the first and the second pretreatment tank, the slurry issubjected to a thermal and alkali hydrolysis. However, the temperatureand/or the pressure is significantly higher in the second pretreatmenttank, which is therefore preferably designed as a closed system capableof sustaining high pressures.

[0172] Finally, the slurry having been subjected to a pre-treatment asdescribed herein above is preferably diverted to at least onethermophile reactor (6) and/or at least one mesophile biogas reactor(6). The slurry is subsequently digested anaerobically in the reactorsconcomitantly with the production of biogas, i.e. gas consisting ofmainly methane optionally comprising a smaller fraction of carbondioxide. The biogas reactor(s) preferably forms part of an energy plantfor improved production of energy from the organic material substrate.

[0173] The biogas can be diverted to a gas engine, and the energygenerated from this engine can be used to heat the stripper tank.However, the biogas can also be diverted into a commercial biogaspipeline system supplying household and industrial customers.

[0174] The remains from the anaerobic fermentation, still in the form ofa slurry comprising solids and liquids, is preferably diverted, in apreferred embodiment, to at feast decanter centrifuge (7) for separatingsolids and fluids. One result of this separation is an at leastsemi-solid fraction comprising almost exclusively P (phosphor), such asan at least semi-solid fraction preferably comprising more than 50%(w/w) P (12). In the same step (7), or in another decanter centrifugeseparation step (8), an at least semi-solid fraction preferablycomprising almost exclusively K (potassium), such an at least semi-solidfraction preferably comprising more than 50% (w/w) K (13) is preferablyalso obtained. These fractions, preferably in the form of granulatesobtained after a drying step, including a spray drying step or a slurrydrying step, preferably comprise P and/or K in commercially acceptablepurities readily usable for commercial fertilisers (10). Suchfertilisers may be spread onto crops or agricultural fields. The liquids(9) also resulting from the decanter centrifuge separation step, such asreject water, can also be diverted to agricultural fields, they can bediverted back to the stable or animal house, or into a sewage treatmentsystem.

[0175] In a further embodiment, the first pretreatment tank may besupplied with organic material originating from silage tanks (4)comprising fermentable organic materials. The divertion of such organicmaterials to the first pretreatment tank may comprise a step involvingan anerobic fermentation such as e.g. thermophilic fermentation tankcapable of removing gasses from the silage. Additionally, straws ande.g. crop wastes originating from agricultural fields (5) may also bediverted to stables or animal houses and later to the first and/orsecond pretreatment tank.

[0176]FIG. 2 illustrates an embodiment essentially as described in FIG.1, but with the difference that only phosphor (P) is collected followingdecanter centrifuge separation, and water in the form of reject water iscollected in a separate tank for further purification, including furtherremoval of N, removal of odours, and the majority of the remainingsolids. This may be done e.g. by aerobic fermentation. Potassium (K) mayalso be separated from the liquids at this stage.

[0177]FIG. 3 illustrates an embodiment comprising a simplified approachto the combined biogas and slurry separation system according to thepresent invention. In this embodiment, no biogas fermentors are used,and the solids resulting from pretreatment in pretreatment tanks one (2)and/or two (3) are subjected to decanter centrifuge separation (4 and 5)following stripping of N including ammonia and collection thereof in aseparate tank (8). Separate and at least semi-solid fractions comprisingP and K are obtained (9 and 10).

[0178]FIG. 4 illustrates an embodiment wherein the potassium (K) is notseparated following decanter centrifuge separation as described for theembodiment illustrated in FIG. 3. Further separation of K from thereject water subsequently collected is however possible.

[0179]FIGS. 5 and 6 illustrate a preferred embodiment of the systemaccording to the invention. The individual components are describedherein in detail.

[0180] Further preferred embodiments of the present invention aredescribed in further detail herein below.

DETAILED DESCRIPTION OF THE INVENTION

[0181] The present invention pertains to a number of individual aspectsas described herein further below.

[0182] The First Aspect (Sanitation)

[0183] The first aspect includes a system consisting of a first device,a house or stable for the rearing of animals including domestic animalssuch as pigs and cattle, and/or a second device mainly for stripping ofammonia and pre-treatment of the substrate and/or a third device mainlyan energy plant for improved production of energy from the substrate.

[0184] The system can preferably consist of an animal house and astripper tank and a biogas reactor. Additional components can include adevice for addition of CaO or Ca(OH)₂ to the slurry, an absorptioncolumn operated on the basis of e.g. sulphuric acid, a storage tank forthe ammonia concentrate, and a storage tank for digested slurry.

[0185] The produced biogas can desirably be used for production ofcurrent and heat in a gas motor and generator, the current preferablybeing sold to a net and the heat preferably used for heating of e.g.slurry and/or animal houses. The energy plant according to the inventionhas an outstanding performance in terms of the energy production perunit substrate treated in the plant. The outstanding performance isachieved by a combination of pre-treatment of the substrate to bedigested, whether animal manures or other organic substrates, withstripping of ammonia from the substrate before anaerobic digestion.

[0186] The advantages associated with the present invention aredescribed in more detail herein below. One central aspect of thesanitation aspect of the invention is a pretreatment comprising—alone orin combination—a number of individual pretreatment steps described indetail in the following:

[0187] Pre-treatment of slurry following removal from the animal housescan include any one or more of the following steps: 1) ammoniastripping, 2) hydrolyses of organic matter, 3) sanitation of the slurry,4) reduction of foam formation, 5) flocculation, 6) precipitation of P,and 7) prevention of struvite formation.

[0188] The working principles are that slurry is diverted from the firstdevice to a stripper tank where ammonia is stripped by means of additionof CaO or Ca(OH)₂, stripping and heat and absorbed in a column beforestored in a tank. At the same time the slurry is subject to a thermaland alkali hydrolysis, preferably by using a lime cooker. Finally thepre-treated slurry is diverted to the third device, consisting of one ortwo thermopile/mesopile biogas reactors, where the slurry is digestedanaerobically under the production of biogas, i.e. gas consisting ofmainly methane with a smaller fraction of carbon dioxide. The biogas isdiverted to a gas engine and the heat from this engine is used to heatthe stripper tank. The current produced is sold to the net.

[0189] As straw and possibly also sawdust is a significant fraction ofdeep litter from cattle and poultry holdings, there is a need for aspecific pre-treatment of these manures before optimal use as substratefor methane production in biogas plants. Lime pressure cookingrepresents one preferred pre-treatment method in this respect. Deeplitter treated by this technology can thus be made available for methaneproduction in a more efficient way and result in an increased biogasproduction. Additionally, it is assured that uric acid and ureadissociates to ammonia and that proteins and other substances aredissolved. It is hereby ensured that the inorganic nitrogen from thedeep litter can be collected in the N-concentrate by the ammoniastripping process.

[0190] The availability of the N in the deep litter and poultry manureto agricultural crops is therefore substantially increased. It isestimated that the potential utilization efficiency can be increased toabout 90% as is the case for the other manures treated in the biogas andslurry separation plant according to the present invention.

[0191] Alternatively, it may be appropriate to digest the poultry manurein the first thermo- or mesopile reactor before passing it to thestripper tank. This depends on the quality of the manure and to whichdegree the uric acid dissociates due to the two different treatments.Experience gained after some working time of the plant shall clarifythis. It is important to stress the versatility of the plant whichallows all types of manure and energy crops to be treated.

[0192] The technical construction is relatively simple because a screwconveyor equipped with a macerator, all made of rust- and acid proofsteel, conveys the biomass into a lime cooker where the mass is heatedby a steam injection to 180-200° C. The pressure becomes 10-16 barduring the 5-10 minutes necessary for the mass to be treated.

[0193] The unit to be constructed shall be able to produce temperaturesand pressures in the temperature interval of 100-200° C. Hereby it ispossible to adjust the treatment to different biomasses to be digestedin the plant according to the invention under due consideration to useof energy, tar formation and technical parameters.

[0194] Foam formation represents a common problem in biogas plants. Onepreferred choice for controling foam formation in biogas plants, inparticular when supplied with large amounts of biomass from e.g. energycrops, is rape oil, which in addition to the effect of foam control alsois a substrate for methane gas formation. Ca-ions are also veryefficient in controlling foam as are many salts. One preferred foamcontrolling measure of the present invention is Ca(OH)₂ and/or CaO inaddition to its other effects mentioned earlier. Supplementing theslurry with Ca-ions is also believed to stimulate the formation offlocks and the bacterial adhesion to organic partides and thus theperformance of the anaerobic digestion.

[0195] Accordingly, if additional foam control and/or flocculation isneeded in the process because of a very high gas production thefermenters may be supplied directly with Ca and/or rape oil. Theaddition of Ca(OH)₂ or CaO will also lead to precipitation ofbicarbonates as CaCO₃. This reduces the CO₂ concentration in solutionand in the gas phase and contribute to the reduction of foam formationthrough reduced carbon dioxide emissions.

[0196] Addition of Ca(OH)₂ or CaO in connection with stripping ofammonia and sanitation of the slurry will also lead to precipitation oforthophosphate, i.e. dissolved P(PO₄ ⁻⁻⁻). These P-particles may besuspended in the slurry as well as other flocks. The use of Ca will alsolead to a limited reduction of chemical oxygen demand (COD), which meansthat Ca precipitates other salts than just the orthophosphate.

[0197] It is believed that—irrespective of the chemical differencesbetween various organic waste products, a simple heat treatment and inparticular heat treatment in combination with alkali hydrolysis willlead to an increased gas yield. Furthermore, a combination of hightemperatures and high pH during pre-treatment is believed to result in amore effective sanitation of the organic material as compared toanaerobic digestion alone, whether thermofile or mesofile.

[0198] It should be noted that in the Statutory Order no. 823 from theDanish. Ministry of Environment and Energy, it is laid down that acontrolled sanitation consists of 1 hour residence time at 700 C. Inview thereof, a treatment according to preferred embodiments of theinvention consisting of one week residence time at 700 C before twosubsequent anaerobic digestions (thermo- or mesofilic) is believed tocompletely eliminate all known veterinary and/or human microbial andzoonotic pathogens. Preferably, BSE prions are also eliminated or atleast significantly reduced in number.

[0199] The overall result is that all infectious organisms in the slurryare eliminated and therefore not spread to the environment when themanure is applied to land. This also makes it possible to flush thefirst device (the animal houses) with the digested slurry in order tomaintain the sties etc. clean. Cross infections among animals are thusprevented. It also allows further use of water to rinse animals andsties, air exhausts etc. with the effects of preventing emissions to airof odour, dust and infectious agents. This is possible because theslurry with additional water shall not be stored till periods where landspeeding is permitted. The slurry without N may be spread to landthroughout the year.

[0200] However, in the first aspect it is the pre-treatment and thus thesterilization of the slurry which is preferred in order to to allowsubsequent spreading onto agricultural fields.

[0201] It will be clear that the present invention relates to a varietyof different aspects, which constitute, individually or in combination,patentable inventions in their own right. The below section contains adescription of various individual parts (components) of one aspect ofthe present invention. An overview of the components are given in FIGS.5 and 6.

[0202] It will be understood that selected components can form the basisfor other aspects of the present invention. The invention shall in noway be limited to the combination of the entire list of componentsdescribed herein below. It will be clear from the description when otheraspects of the invention are related to only some of the componentsdescribed herein below. Non-limiting examples of such aspects includesdevices for concentration of N (nitrogen) and/or P (phosphor) and/or K(potassium); energy generation based on the components of stripper tank,lime cooker and fermentor; and animal welfare/reject water processing.

[0203] It will also be understood that the below aspects related—amongother things—to the aspect of sanitation, does not necessarily have tocomprise all of the components illustrated below. Aspects related tosanitation are also understood to cormprise a combination of only someof the components described herein below.

[0204] Animal Houses

[0205] The animal houses (Component number 1) serves to provide anoptimal food safety and food quality, an optimal animal welfare andworking conditions for the labour personal in the housings, an optimalslurry management, suitable for treatment in the GreenFarmEnergy plant,and a reduction of emissions to the external environment to a minimum(ammonia, dust, odour, methane, dinitrogen oxide and other gasses).

[0206] The housing system can consist of one or more early weaninghouses with a total of 10 sections designed to produce 250 livestockunits annually. Each section houses e.g. 640 piglets (7-30 kg) or 320slaughter pigs (30-98 kg).

[0207] An amount of about 10.000 m3 slurry can be expected to beproduced annually. In addition to this volume an amount of 5-10.000 m3process water shall be recycled through the houses. The following mainconditions shall preferably be met by the housing system:

[0208] 1) Two-climate system: The sties shall preferably be designed astwo-climate systems. The back end of the sties shall be equipped with anadjustable coverage providing an opportunity for the pigs to choosebetween a relatively warm environment under the covering and arelatively cold environment in the rest of the sty. The temperaturedifference shall be in the range of 5-10 deg. C.

[0209] When the piglets have grown to around 30 kg the coverage shall beused to allow for generally colder temperatures in the animal house assuch. The pigs may keep warn under the coverage. By allowing for coldertemperatures it is possible to increase ventilation also during colderambient periods.

[0210] 2) Occupation: The pigs are preferably offered straw from anautomate. The searching and digging behaviour is hereby stimulated,because they shall pick out the straw from the automate by themselves.The straw serves also as an energy source in the energy plant.

[0211] 3) Heating: Heat from the energy plant is preferably recyded tothe animal houses. The heat can be provided by two separate circulationsystems. One is located under the covering to 30-35° C., which providesthe pigs with a comfortable micro-climate, keeps the floor dry andreduces bacterial growth on the floor. The second provides heat to theoverall airspace in the house via pipes along the walls of the house.The second circulation is coupled to the ventilation control.

[0212]4) Showers: Showers are preferably established over the slats.which covers ¼ of the total floor area. This motivates the pigs tomanure on the slats. as opposed to the solid floor. The shower waterwill flush the manure into the canals preventing malodour, ammonialosses etc. The clean solid floors substantially reduces the possibleinfections form pathogens in the manure as Slamonella, Lavsonia etc.

[0213] 5) Flushing: The manure canals are preferably flushed severaltimes a day. It is provided by flushing of canals with process waterfrom the energy plant. The manure is diverted to a central canal througha valve.

[0214] 6) Canal design: The surface of the manure is reduced by use ofV-shaped canals and an optimal flushing of the canals are achieved atthe same time. This is central for the reduction of emissions from theanimal houses.

[0215] 7) Ventilation: The ventilation is designed so that 20% of themaximum ventilation is diverted down under and through the slats. intocentral ventilation shack. between the double V-canals. In 60-80% of theyear 20% of the maximum ventilation is sufficient to provide ambleventilation.

[0216] 8) Feeding: Foodstuff is provided by a wet feeding equipmentwhich provides fodder ad libitum.

[0217] SlurrY Collection Tank

[0218] The function of a slurry collection tank (Component number 2) isto collect slurry form the daily flushings of the animal houses and towork as a buffer before pumping to the main reception tank. The slurryis diverted to the collection tank by means of gravitation. The volumecan be anything appropriate, such as e.g. 50 m³. The tank can be made ofconcrete and it can be placed below the floor in the animal houses sothat the slurry form the houses can be diverted to the collection tankbe means of gravitation.

[0219] Main Reception Tank

[0220] Slurry from the collection tank is preferably pumped to the mainreception tank (Component number 3). Other types of liquid manure/wastemay also be added to the reception tank from other farms/plants. Optionsare mink slurry, cattle slurry, molasses, vinasses, silage etc. This istransported to the reception tank by lorry and is loaded directly intothe reception tank. The volume/capacity is anything appropriate, such ase.g. about 1.000 m³. The level in the stripper tank preferably controlsa pump, which pumps slurry from the reception tank. The dose adjustmentcan be manual or automatic. The maximum capacity can be anythingappropriate under the circumstances.

[0221] CaO Addition

[0222] When slurry is being pumped from the reception tank 1 to thestripper tank, lime is added to the slurry in order to increase the pH.The lime addition manifold is preferably adjusted to add 30-60 g CaO/kgTS. The lime is preferably supplied as a powder which can be blown intothe silo from the lorry. The volume/capacity of the silo can be e.g.about 50-75 m³. The dose of 30-60 g/kg TS corresponds to app. 6-12 kgCaO per hour with a slurry capacity of 3.5 m³/h with 6% TS.

[0223] When added directly to the slurry (6% TS), the lime dose is about60 g/kg TS yield (about 8.8 kg CaO per hour). It is however preferred toadd the lime directly to the alkali pressure sterilazation andhydrolysis unit. When lime is added directly to the pressure unit (theE-media hold 2G-70% TS), the lime dose is about 30-60 g/kg TS. 60 g 1 kgd.m. equals about 342 kg CaO per batch, while 30 g/kg d.m. equals about171 kg CaO per batch.

[0224] Balance Installation

[0225] The balance (Component number 5) shall preferably weigh theincoming E-media (energy containing organic material). The supplierswill preferably specify the type of media which is supplied to theplant, i.e. deep litter, energy crops etc. of various sorts.

[0226] The specification shall be made by selecting the relevant E-mediaon a control panel. According to the suppliers panel registration, theweight of received E-media incl. specification of media is recorded.

[0227] The control thus specifies for each E-media (see alkalihydrolysis):

[0228] Energy potential

[0229] The required heating time

[0230] The required retention time

[0231] Reception Station for Deep Litter and Energy Crops

[0232] The reception station (Component number 6) shall receive deeplitter from e.g. poultry or other animals as well as energy crops. Thestation is preferably a large silo equipped with several screw conveyorsin the floor. The lorries will empty their load of E-media directly intothe silo. The volume/capacity can be anything appropriate under thecircumstances, such as e.g. a yearly capacity of E-media (about 51.5%TS) of about 9.800 tonnes. The volume of the silo can be from severalcubic meters to about 100 m³, corresponding to three days capacity (65h). The materials are preferably concrete/steel.

[0233] Silo for Energy Crops

[0234] The silo for energy crops (Component number 7) serves to providestorage means for energy crops. The crops are preferably conserved assilage. The volume/capacity can be e.g. from about 5.000-10.000 m⁸. Thesilo can be a closed compartment from which silage juice is collectedand pumped to the reception tank.

[0235] Transport- and Homogenisation System for Deep Litter and EnergyCrops

[0236] The transport- and homogenisation system (Component number 8) fordeep litter and energy crops preferably receives E-media from the screwconveyors in the floor of the reception station. The E-media can betransported by additional screw conveyors to the cooking units and atthe same time preferably macerated by an integrated macerator. Thevolume/capacity can be anything required under the circumstancesincluding about 1.5 m3 E.media/hour, or 8.200 tonnes of E-media/year.The capacity of the transport- homogenisation system is preferably notless than about 30 m3/hour. Three fundamental parameters shall controlthe addition of E-media, i.e. volume, weight per volume, and time. Fromthese parameters volume per unit time, time and thus total volume andweight shall be established.

[0237] Alkali Pressure Sterilization and Hydrolysis Unit

[0238] The alkali pressure sterilization and hydrolysis unit (Componentnumber 9) shall serve two main purposes, i.e. firstly elimination ofmicrobial pathogens in the E-media in particular in deep litter fromvarious poultry or other animal productions and secondly, at the sametime hydrolyse structural components of the litter in order to renderthem available for microbial degradation in the fermentors.

[0239] The unit shall also preferably eliminate or at leastsubstantially reduce BSE-prions if present in waste introduced into theplant. Such waste include flesh- and bone meal, animal fats or similarproduce from the processing of animals not used for consumption.

[0240] Filling of the pressure sterilizer is provided by the transport-and homogenisation system, which transports E-media into the accordingto type of E-media as defined on the balance installation.

[0241] The pressure cooking unit consists of two identical units, i.e.,two elongated pipe-like horizontal chambers with a central screw. Thetwo pipes are fastned one on top of the other in order to provide foreasy loading of the lower pipe. The units are covered by a hollow capeon the downwards side. The cape shall divert heat to the media fromsteam under the cape.

[0242] Lime is added to the upper cooking unit from the CaO silo, i.e.,342 kg per batch.

[0243] The lower pipe receives pre-heated E-media from the upper unit.

[0244] The lower unit is emptied into a small mixertank containing 25m³. Here the E-media is mixed with slurry from the reception tank 1, themixture is subsequently pumped into the strippertank.

[0245] The CaO tupe contains a by pass so that CaO can be added directlyinto mixing container under the two pipes. The mixing chamber is usedfor mixing sterilized E-media and raw slurry from the reception tank toprovided a homogeneous biomass and to reuse the heat of the E-media.

[0246] The central process parameters are dry matter content of theE-media, temperature, pressure and pH. From a wide range of possiblecombinations the optimal parameter setting is a temperature of 160° C.,pressure of 6 bar, dry matter content og app. 30%, and pH of app. 12.

[0247] The retention time in the sterilization unit consists of severalphases: 1. Filling time; 2. Preheating time in the upper pipe; 3.Heating time in the lower pipe; 4. Retention time at the selectedtemperature and pressure; 5. Pressure release time; 6. Emptying time,and 7: CIP time

[0248] The filling phase consists of the time required to transport theE-media into the pressure sterilizer and mix it with the added slurry.The filling time shall be app. 10 min. After filling the E-media shallbe heated to 160 C at 6 bar. Preheating takes place in the upper pipeand final heating in the lower pipe. Heating time is expected to be app.30-40 min.

[0249] The retention time at the desired temperature and pressure shallbe app. 40 min (at 160 C and 6 bar).

[0250] Pressure release time app. 10 min. The pressure is released intothe stripper tank.

[0251] Emptying is achieved by running of the screw conveyors.

[0252] CIP time. Cleaning performed on occasion, generally notnecessary.

[0253] The volume of the pressure cooker is 10 m³ per unit, and thedegree of filling is app. 75-90%. The volume of the mixing container is25 m³.

[0254] An example of running conditions are illustrated below. RangeSelected Units TS 10-30 30 % of total weight Temperature 120-160 160 °C. Pressure 2-6 6 Bar PH 10-12 12 pH

[0255] At the panel for suppliers where E-media are registrated thefollowing shall preferably be defined for the control of thesterilization unit: Weight, volume and sort of E-media. It is thuspossible to define for each E-media transported to the pressure cookerthe:

[0256] Energy potential for each E-media

[0257] Necessary heating time

[0258] Necessary retention time

[0259] Necessary mixing time with the slurry

[0260] Necessary energy use depending on E-media

[0261] Degree of filling, signal from radar/microwave gauge

[0262] Empirical based values depending on visual monitoring by theoperator

[0263] Mixinq Tank for Pressure-Sterilized E-media and Raw Slurry

[0264] Following sterilization and hydrolysis in the pressure unit, thetreated biomass is allowed to expand into a mixingtank (Component number10) preferably located below the pressure unit. Excess pressure (steam)is released into the strippertank in order to collect ammonia andtransfer heat to the stripper tank biomass before expansion into themixertank.

[0265] The purpose of the mixertank is to mix cold raw slurry from thereception tank with hot sterilized E-media in order to obtain heattransfer (re-use of heat) and mixing of the two media.

[0266] The volume/capacity is e.g. about 25 m³. Any suitable materialcan be used, including insulated glasfibre. The working temperature istypically about 70-95° C.

[0267] Tank for Liquid Biomass

[0268] The liquid biomass contained in the tank for liquid biomass(Component number 11) shall be use to ensure sufficient biogasproductionduring the start up phase of the whole plant. However, it can also beused occasionally, when such liquid biomass is available. Liquid biomassinclude e.g. fish oil, and animal or vegetable fats. Vinasses andmolasses can also be used, but this is not preferred because of therelatively high water content and thus low potential energy content perkg product.

[0269] The volume/capacity is typically about 50 m³, and a suitablematerial for the tank is stainless steel. The contents of the tank ispreferably liquids and solids having a particle size of max. 5 mm.Stirring as well as a heating system for temperature control ispreferably provided, as are feeding pump(s) to the fermentor(s). Thetemperature shall preferably be min. 75° C. so that oily or fattybiomass can be pumped into the fermentor(s).

[0270] Stripper and Sanitation Tank

[0271] The stripper and sanitation tank (Component number 12) preferablyreceives the following media:

[0272] Slurry from reception tank 1 and/or

[0273] E-media from the pressure cooker, and/or

[0274] Possibly liquid biomass from biomass liquid tank, and/or

[0275] Reject water from decanter or possibly after K-separation.

[0276] The purpose of the tank is to regenerate heat used in thepressure cooker by heating the slurry from reception tank 1, to mix theE-media with slurry and hence to produce a homogeneous feed to thefermentors, to control pH before feeding to fermentors, and to sanitisethe slurry.

[0277] The stripper and sanitation tank strips ammonia, step I, and thegas is diverted to an absorption column which is common to the finalstripper process, step II. Microbial pathogens are eliminated and themedia/slurry is prepared for anaerobic digestion.

[0278] One presently preferred shape of the stripper and sanitation tankis:

[0279] Bottom/floor

[0280] With insulated concrete cone, directed downwards angle 20 degrees

[0281] Impaired stirring/sand is removed from the floor or according tothe mammut pumping system

[0282] A sand filter is placed in the bottom, which can be emptiedthroughout an external pipe connection. It will also be possible toempty the tank through the filter

[0283] Top/ceiling

[0284] With cone construction of sandwich insulated IsofatalicPolyesters (Encapsulated Foam). Cone angle is approximately 10 degrees.

[0285] Mounted water drizzle system to avoid the production of foam fromthe stirring process and the process in common.

[0286] A slow running stirring system is placed on top of cone to toensure the optimal homogenisation,-optmal vaporation of the ammonia, andoptimal distribution of heat in the media.

[0287] The ammonia is transported through wet air in a pipe to theabsorbing unit

[0288] Side/wall

[0289] With cylinder construction of sandwich insulated IsofatalicPolyesters (Encapsulated Foam).

[0290] Mounted approximately 600 meters of heating {fraction (5/4)}″pipes in a cylinder ring shape inside the tank to heat up the media

[0291] Mounted some temperature transmitters to regulate the heatingprocess

[0292] Mounted a pH-measuring instrument to regulate the acid supply tothe media

[0293] Outside cylinder wall at the bottom is mounted a insulatedvalve/pumping room

[0294] An ammonia steam diffuser is placed in the middle of the tank.The ammonia steam generated in the alkali sterilisation and hydrolysingunit is diffused into the media.

[0295] Volume/Capacity: The cylinder wall has an inside diameter ofabout 12 m and a height of 9 m. This means a tank handling volume ofapproximately 1.000 m³ the bottom cone included.

[0296] The hydraulic retention time for slurry and E-media is about 7days, and the absolute minimum retention time is about 1 hour.

[0297] In one preferred embodiment, the bottom is basically made ofconcrete, arming iron and pressure proof insulation. The surface incontact with media is coated with isofatalic Polyester to avoidcorrosive damaging of the concrete and arming iron. All pipes mounted inthe bottom is either polyester or stainless steel. The top and bottom isbasically a construction of sandwich insulated Isofatalic Polyesters(Encapsulated Soap). All pipes mounted is either polyester or stainlesssteel.

[0298] Other Components

[0299] The stirring element is made of stainless steel

[0300] The heating elements is made of coated mild steel and/orstainless steel

[0301] All other components placed inside the tank is made of stainlesssteel

[0302] In one preferred embodiment, default parameter values forstripping of ammonia from slurry in this system are: Temperature ofabout 70° C.; pH of about 10-12; liquid gas ratio of <1:400, 1 weekoperation, and more than 90% affectivity is achieved.

[0303] An example of conceivable running conditions are listed below:Media: All sorts off liquid animal manure and pres- sure sterilizedsolid or liquid E-media, vari- ous liquid organic wastes, CaO. Runningtemperature: 70-80° C. Running gas combination: 80% NH₄, 15% CO₂, 3% O₂,2% other gases Insulation k-value: 0.20 W/m²K Running Max. Pressure: +20mbar abs. (No vacuum) Max. viscosity in media: 15% TS Base/Acid-range:5-10 pH Abrasive rudiments in 1-2% Media (Ex. Sand): Max. temperature inheat- 90 degrees celcius ing elements: Max. effects in heating 600 kWelements: Transmission effect: 7.5 kW/20-25 rpm.

[0304] The stripper and sanitation tank supplies the fermentor(s) withtreated material for fermentation. In a timed process the material willbe transported to the fermentors. The demand of material depends on thedigestion process in the fermentors. One, two, three or more fermentorscan be employed.

[0305] The stripper and sanitation tank is regularly filled with slurryand E-media from the alkali pressure process. Finally, to obtain a drymatter of ˜15% (15% TS). Some level switches regulate the content in thetank. A TS-mesuring unit regulates the content of TS. Every 1 hour afterfilling of slurry and E-media it is possible to pump E-media to thefermentor(s).

[0306] The top of the stripper and sanitation tank is preferablyventilated through an ammonia-absorbing unit (Step I), and apH-measuring unit regulates the need for CaO.

[0307] The temperature of the E-media is regulated through temperaturetransmitters.

[0308] A timed process can optionally pump water/slurry into the drizzlesystem to prevent production of foam.

[0309] Fermentors for Biogas Production

[0310] Digestion of the biomass is provided by a multi-step fermentorsystem preferably comprising three fermentors (Components 13, 14 and15). Systems with fewer as well as more fermentors can also be applied.

[0311] The fermentors are preferably connected to achieve maximumflexibility and optimum biogas production. The fermentors shall beplanned for routinely running at termofile (45-65° C.) as well asmesofile (25-45° C.) temperatures.

[0312] The digestion process can be optimised in terms of organicloading rate, retention time, and maximum digestion (min. 90% of VS).Heat spirals are included in order to heat the biomass to the preferredrunning temperature.

[0313] A top fastened slow running stirrings system ensures optimalhomogenisation and distribution of heat in the biomass.

[0314] Regulation of pH is possible through addition of an organic acid(liquid) in necessary quantities.

[0315] The fermentors preferably receives the following media:

[0316] E-media from the stripper and sanitation tank

[0317] Liquid biomass from the liquid biomass tank

[0318] Acids from the acid tank

[0319] The specific shape of the tank can in one preferred embodimentbe:

[0320] Bottom/floor

[0321] With insulated concrete cone, directed downwards angle 20 degrees

[0322] Impaired stirring/sand is removed from the floor or according tothe mammoth pumping system

[0323] A sand filter is placed in the bottom, which can be emptiedthroughout an external pipe connection. It will also be possible toempty the tank through the filter

[0324] Top/ceiling

[0325] With cone construction of mild steel. Cone angle is approximately10 degrees

[0326] Mounted water drizzle system to avoid the production of foam fromthe stirring process and the process in common

[0327] A slow running stirring system is placed on top of cone to toensure the optimal homogenisation, and optimal distribution of heat inthe media.

[0328] The biogas is transported through wet air in a pipe to thegasbag.

[0329] Side/wall

[0330] With cylinder construction of mild steel.

[0331] Mounted approximately 600 meters of heating {fraction (5/4)}″pipes in a cylinder ring shape inside the tank to heat up the media

[0332] Mounted some temperature transmitters to regulate the heatingprocess

[0333] Mounted a pH-measuring instrument to regulate the acid supply tothe media

[0334] Outside cylinder wall at the bottom is mounted a insulatedvalve/pumping room

[0335] The volume/capacity of each tank canhave any suitable net volume,including a net volume of about 1.700 m³.

[0336] The materials for the fermentors can e.g. be as specified below:

[0337] Bottom

[0338] The bottom is basically made of concrete, arming iron andpressure proof insulation

[0339] The surface in contact with media is coated with IsofatalicPolyester to avoid corrosive damaging of the concrete and arming iron

[0340] All pipes mounted in the bottom is either polyester or stainlesssteel

[0341] Top and wall

[0342] The top and wall is basically a construction of mild steel

[0343] All pipes mounted is either polyester, stainless steel or mildsteel

[0344] Other components

[0345] The stirring element is made of mild steel

[0346] The heating elements is made of mild steel

[0347] All other components placed inside the tank is made of stainlesssteel or mild steel

[0348] The running conditions can be any conditions suitable, includingMedia: All sorts off animal manure, primarily pigs slurry. Maceratedenergy crops. Some sorts of organic waste, CaO, organic Acids Runningtemperature: 35-56° C. Running gas combination: 65% CH₄, 33% CO₂, 2%other gases Insulation k-value: 0.25 W/m²K heatloss is estimated to 10kW Running Max. Pressure: +20 mbar abs. (No vacuum) Max. viscosity inmedia: 12% TS Base/Acid-range: 5-10 pH Abrasive rudiments in 1-2% media(Ex. Sand): Max. temperature in heat- 80 degrees celcius ing elements:Max. effects in heating 600 kW elements: Transmission effect: 7.5kW/20-25 rpm

[0349] The digestion shall be run at about 55° C. Heat loss is estimatedto about 10 kW. The biomass in the tank is can be heated from 5° C. to55° C. during 14 days, and the possibility of addition of acid foradjustment of pH.

[0350] Tank for Organic Acids for pH Adjustments in Fermentors

[0351] A tank for organic acids (Component number 16) for pH adjustmentsin the fermentor(s) is preferably also provided.

[0352] Buffer Tank for Degassed Slurry Before Decanter

[0353] Following digestion of the biomass in the fermentors the degassedbiomass is pumped to a small buffer tank (Component number 17) beforebeing subjected to separation in the decanter.

[0354] Decanter Installation

[0355] The function of the decanter installation (Component number 18)is to extract suspended solids (ss) and P from the biomass.

[0356] The decanter separates the digested biomasse into the twofractions i) solids, including P, and ii) reject water.

[0357] The solids fraction contains 25-35% d.m. App. 90% of the ss. and65-80% of the P-content of the digested biomass is extracted. In case ofaddition of PAX (Kemira Danmark) to the buffer tank before separation inthe decanter, app. 95-99% of the P can be extracted. The solids fractionis transported to containers by means of a shaft less screw conveyor.

[0358] The rejectwater contains 0-1% ss and dissolved K. The ss dependson the addition of PAX. The principal component of the reject waters isdissolved K which amounts to app. 90% of the original K-content in thebiomass. The reject water is pumped to the reject water tank.

[0359] P-Fraction Transport System and Treatment

[0360] From the decanter installation the solid matter fraction(routinely called the P-fraction) can be transported to a series ofcontainers by means of conveyor screws and belts forming a P-fractiontransport system (Component number 19).

[0361] A common conveyor band transports P-fraction to a storage whereit is stacked into miles, covered with a compost sheet and allowed tocompost. The composting process further dries the P-fraction and thed.m.-content thus increases to 50-60%.

[0362] Second N-Stripping Step

[0363] Efficient stripping of ammonia from the reject water ispreferred, and a residual level of about 10 mg NH₄—N/ltr or less ispreferred.

[0364] The second stripping step is preferably carried out by using asteam stripper operated at ambient pressure. The stripper principlebenefits form the different boiling temperatures of ammonia and water.At temperatures close to 100 ° C. extraction of ammonia is mostefficient. The use of energy in order to heat the feed is an essentialrunning parameter. The stripper unit shall therefore preheat the feedbefore entering the stripper column to close to 100° C. This is providedby use of steam (or possibly warm water and steam) from themotorgenerator unit in a steam-water heat exchanger.

[0365] When heated the feed enters the stripper column and percolatesover the column while at the same time being heated to the runningtemperature by a counter current of free steam. The steam/ammonia gas issubsequently condensed in a two step condensator.

[0366] From the floor of the column the water now free of ammonia ispumped to a level controlled exit pump.

[0367] The stripped ammonia is diverted to the bottom of a two-stepscrubber condensator where the ammonia gas is condensed primarily in acounter current of cooled ammonia condensate. The ammonia gas notcondensed are subsequently condensed in a counter current of pure water(possibly permeate from the final reverse osmosis step). If the use ofacid is wanted or necessary it is appropriate to use sulphuric acid atthis stage. It is thus possible to achieve a higher final concentrationof ammonia.

[0368] The scrubber condensator are preferably constructed from apolymer in order to allow the use of acids.

[0369] Ammonia Absorption Column (for Use With First and/or SecondN-Stripping

[0370] A condensate scrubber is used in order to gain flexibilityconcerning addition of add. The column (Component number 21) ispreferably constructed in two sections so that the fraction of ammonianot condensed in the first section is subsequently condensed in thesecond section. This takes place in a full counter current so thataddition of water is limited as much as possible. Thereby a maximumammonia concentration in the final condensate is reached (larger than25%). The ammonia product can be pumped out with a separate pump or betaken out from a valve on the circulation pump. The absorption may beassisted by addition of sulfuric acid into the water counter current.

[0371] Sulphuric Acid Tank

[0372] The sulphuric acid tank is used for storing the sufuric acid usedin the N-stripping process. (Component number 22).

[0373] NS Tank

[0374] The NS tank (Component number 23) is used for storing thestripped N.

[0375] Gas Store

[0376] It is preferred to establish a gas store (Component number 24) asa bufferstore for the feeding of e.g. a motorgenerator engine.

[0377] Rejectwater Tank

[0378] From the decanter installation the rejectwater is preferablypumped to the rejectwater tank (Component number 25).

[0379] The rejectwater tank is equipped with a submerged micro-filterwith static operation. The micro-filter shall remove particles largerthan 0.01-0.1 μm. A negative pressure of 0.2-0.6 bar shall be built upat the membrane. Hence the permeate is sucked through the membraneretaining the particles on the membrane surface. In order to preventmembrane fouling and scaling the coating of the membrane surfaces has tobe removed by a periodic backwash procedure.

[0380] A micro-processor control device shall automatically control theextraction of permeate and the backwash procedure. The extraction shallbe interrupted by periodic backwash e.g. for 35 seconds for every 300seconds running time. The total flow shall be 2-6 m3 per h.

[0381] Aeration may be applied to assist the micro-filtration. Aerationimpose shear stress on the membrane surface reducing scaling andfouling. It further aerates the rejectwater and stimulates aerobicdecomposition of residual organic matter, nitrification anddenitrification. Possible remaining odour, nitrate etc. is thus removedduring the process of micro-filtration.

[0382] From this tank the permeate shall be used for:

[0383] Rinsing of the animal houses, canals, slats etc.

[0384] Further separation. Dissolved K shall be concentrated by means ofreverse osmosis, the K-fraction being stored in a separate storage tank.Water for rinsing animals houss may also be taken form this permeateflow.

[0385] The K may also be concentrated through other means such asmechanical or steam compression. This depends on the specific choice foreach specific plant and amount of excess heat available for steamcompression.

[0386] The reject water tank containing the concentrate from themicro-filtration shall be emptied at regular intervals to remove theparticle concentrate. This shall be added to either the K-fraction orthe P-fraction from the decanter.

[0387] K Tank

[0388] The K tank (component number 26) serves the purpose of storingthe potassium (K) concentrate.

[0389] Gas Cleaning

[0390] The biogas produced in the fermentors may contain trace amountsof hydrogen sulfide (H₂S) which are necessary to remove (Componentnumber 27) before burning the biogas in a combined heat and power plant.

[0391] The gas shall be cleaned by employing the ability of certainaerobic bacteria to oxidise H₂S into sulfate. The genus shall primarilybe the genus Thiobacillus which is known form several terrestrial andmarine environments. Other genus may also be used such as Thimicrospiraand Sulfolobus.

[0392] A tank made of glass fiber packed with plastic tubes with a largesurface area shall be rinsed with reject water to maintain the packingmaterial moist. The biogas is diverted through the packed column and anair stream (of atmospheric air) is added to the biogas stream. Theatmospheric air is added to provide an oxygen concentration of 0.2% inthe gas stream, i.e. sufficient to oxidize the H₂S and therefore not toproduce an explosive mixture of biogas and oxygen. A ring side blower isused.

[0393] Combined Heat and Power Plant (CHP)

[0394] The main component in the CHP (Component number 28) can be e.g. agas fired engine connected to a generator for production of electricpower. The main priority for the CHP is to produce as much electricpower as possible relatively to heat. The engine is preferably cooled bya water circuit (90° C.) and the heat is used in the plant process andto the heating of e.g. the animal houses.

[0395] The exhaust gas is used in a recuperator for steam production.The steam is used as heating source in the plant process, i.e. in thepressure sterilization unit and in the n-stripper unit II (priorityone). Depending on the amount of steam it may also be used forconcentrating the K in the rejectwater (seam evaporation).

[0396] Between the steam and heat circuit, there will be installed aheat exchanger, so it is possible to transfer heat from the steam systemto the heat system.

[0397] In addition to the above mentioned genset there will be installeda steam boiler. This boiler will be used for heat production to startthe process, and in addition be used as a backup for the genset.

[0398] If there is produced more steam than needed in the plant process,the rest production can be flashed of in a cooler.

[0399] To start the plant process (heating of fermentor tanks) etc.,heat is provided by the oil fired boiler. As soon as gas production isachieved the oil burner will be switched to a gas burner. As soon as gasproduction is large enough to start the engine, the engine will takeover the heat production.

[0400] Potassium Separation

[0401] At least two alternatives for separating potassium from therejectwater are possible (Component number 29). At relatively highlevels of biogasproduction the motorgenerator engine produces excessheat (steam at 160° C.) which can be used to concentrate the K. Thedistillate free of nutrients may be used for field irrigation orrecycled through the whole plant.

[0402] At relatively low rates of biogasproduction a micro-filter can beused to filter particles larger than 0.01-0.1 ym from the reject waterrendering the permeate suitable for treatment in a standard reverseosmosis filter. The K shall preferably be concentrated to a 10-20%solution.

[0403] The Second Aspect (BSE Prions)

[0404] In the second preferred aspect the invention may be applied tosubstantially reduce and/or eliminate BSE prions contained in manures,fodder, slaughterhouse waste, flesh and bone meal and the like. This isachieved by a combination of pre-treatment and digestion. Thiscomponents as listed above are supplemented with a device for additionalpre-treatment of the substrate containing BSE prions, e.g. a limepressure cooker. The lime cooking can be used to hydrolyse a variety oforganic substrates including material containing prions.

[0405] BSE prions are proteins resistant to protease attack. However, iftreated with lime at temperatures of preferably 140-180° C., pressuresat preferably 4-8 bar, and a pH of about 10-12 the prions are partlyhydrolysed and thus rendered decomposable by microbial enzymes such asproteases, amidases etc. The microbes are present in the bioreactors andbecause the substrate is stripped for ammonia and thus low in total Nversus total carbon the micro organisms are prone to produceadditionally extracellular proteinases and proteases capable ofhydrolysing the BSE prions. The high residence time also contributes toan efficient decomposition of BSE prions.

[0406] The Third Aspect (Concentration of N and P)

[0407] In a third preferred aspect, the invention may be applied toseparate the main nutrients nitrogen (N) and phosphorus (P) from animalmanures and refine the nutrients to fertilizer products of commercial or“organic” quality. This is achieved by combining the components of thefirst aspect with a decanter centrifuge.

[0408] The N and P are the main nutrients in the slurry which are oftenin excess in animal holdings. The N is stripped and collected asdescribed in the first aspect leaving P in the remaining digestedslurry. However, if subject to a decanter centrifuge, the P is removedfrom the slurry along with organic and inorganic solids.

[0409] The result being that preferably more than 90% of the N and P inthe slurry are collected in separate fractions. The remaining rejectwater contains some potassium (K) and trace amounts of N and P. Thereject water is thus suitable for land spreading at all times of theyear.

[0410] It is possible to extract potassium (K) from the reject water byan additional coupled membrane aeration and filtration. Briefly, ceramicmicro-filters are used as diffusers and filters at the same time. Thefilters are submerged in the reject water and operated with intermittentaeration and filtration periods. Aeration provides decomposition of theremaining organic matter and settling of inorganic flocks. The treatedwater is thus suitable for membrane filtration because fouling andscaling is prevented. Also the aeration through the same membranes (airback flushing) prevents the membranes from fouling and scaling.

[0411] The product produced is a concentrate (mainly containing K) andfiltered water suitable for land spreading (a very limited area isrequired).

[0412] As under the first aspect the reject water may also bere-circulated through the animal houses.

[0413] The P fraction is suitable to further drying, which produces agranulate of commercial value. The N and K fractions are similarly ofcommercial value.

[0414] The third preferred aspect is in particular designed toconcentrate the main nutrients N and P (and K) contained in slurry andother organic substrates to fertilizer products of commercial quality.

[0415] However, if decanter centrifuges are combined with the otherelements of the GFE biogas and slurry separation system, in particularthe N-stripping unit, it becomes of major interest to farmers. Thecombination of the N-stripping and decanter centrifuges means that themajority of the N and P content of the slurry is separated and collectedinto individual fractions. It is important to stress that the P whenpresent in flocks is bound to be stripped by the decanter centrifuge.

[0416] They can be used and added to the fields according to thespecific need of each nutrient It is also possible to re-circulate thereject water taken behind the decanter centrifuge through the animalhouses. Cleaning of floors and slats in the sties are achieved as isadditional advantages in terms of good indoor climate, reduced ammoniaand other gas emissions, frequent flushing of slurry canals etc.

[0417] The reject water may contain a major fraction of the potassium(K), while a smaller part will be present in the P-fraction. This meansthat in the scenario where slurry is stripped for ammonia and separatedfor P the N and P can be stored and applied according to specific needs,while the reject water can be applied throughout the year as wastewater.

[0418] It can be estimated that the need of spreading area is about ¼ ofthe area required for slurry application, the harmony area, and thatthis ¼ part shall run through the whole harmony area over a 4-yearperiod.

[0419] Irrespectively of the possibility of treating the reject waterfurther (see section) some farmers will undoubtedly be more than contentwith the N-and P-stripping with just one single reactor for digestion ofthe slurry. Even the P-stripping by the decanter centrifuge may beomitted because the N is concentrated leaving a dilute slurry without Nwhich may also be spread onto land a any time of the year, except onfrozen land.

[0420] It is very satisfying that parts of the total system can beoffered to farmers while others may be content with any combination moresuitable to their situations. In any case it is the N-stripping whichmake the use of decanter centrifuges interesting to practical farming.

[0421] The reject water from the complete process may be subjected to afinal treatment depending on the market preferences.

[0422] Thus, the challenge is to treat the reject water to becomesuitable for membrane filtration and also larger volume reductions thanthe 50-60% mentioned. The challenge is also to use well known, cheap androbust technologies in a new context.

[0423] The solution is the following:

[0424] Aeration of slurry is well known and aeration with atmosphericair during 24 weeks produces an aerobic digestion.

[0425] Aeration achieves the following:

[0426] First, remaining ammonia is stripped and collected in anabsorption column (possibly the same as the one used duringpre-treatment) by a so-called low-temperature stripping of about 20° C.A wider liquid-gas ratio is required of about 1:2000 (Liao et al. 1995).

[0427] Secondly remaining organic matter and smell components aredecomposed (Camarero et al. 1996; Burton et al 1998; Doyle and Noue1987; Garraway 1982; Ginnivan 1983; Bloun et al. 1988).

[0428] Thirdly possible remaining ammonia after stripping will benitrified to nitrate (Argaman Y. 1984; Gönenc and Harremoës 1985).

[0429] This aeration shall be combined with filtration by employing newsewage waste technology, i.e., a micro-filtration principle combiningaeration and filtration over ceramic filters (Bouhabila et al. 1998;Scott et al. 1998; Zaloum et al. 1996; Engelhardt et al. 1998). Anenergy efficient aeration and filtration is achieved in one operation.The aeration is further used for cleaning of the ceramic membranes by“air back flushing” (Visvanathan et al 1997; Silva et al 2000).

[0430] This leaves a water phase well suited to separation over standardosmosis membranes if necessary, because possible scaling and foulingproblems are minimal. It is therefore hypothesized that a larger volumereduction can be achieved at substantial lower energy costs, althoughsome energy is used for the aeration.

[0431] Even if membrane filtration is not used, aeration it self may bemotivated by the final stripping of ammonia and by removal of theremaining smell components.

[0432] The Fourth Aspect (Renewable Energy)

[0433] The main devices of this preferred aspect are pre-treatmentfacilities consisting of a stripper tank and a lime cooker, and aflexible and multi step (minimum 3-step) process design of bioreactors.

[0434] In the fourth preferred aspect the invention may be applied toproduce large amounts of biogas from a wide range of organic substratesincluding all types of animal manures, energy crops, crop residues andother organic wastes.

[0435] The pretreatment facilities of first and second preferred aspectsallow the use of a variety of organic substrates while the multi-stagebiogas plant allows a complete digestion of the substrate and thus amaximum energy yield.

[0436] N-rich and recalcitrant substrates such as poultry manure anddeep litter is pretreated in the lime cooker. The cooked substrate ispre-digested in a mesopile reactor before the substrates enters thestripper tank and the subsequent reactors.

[0437] The pre-digestion ensures that the readily available organicmatter is decomposed and the N released into solution as ammonia. Thebulk of the N is thus is thus collected in the stripper tank and therecalcitrant organic substrate being decomposed in the subsequentreactors of the energy plant. Alternatively, depending on the quality ofthe substrate, it may enter directly into the stripper tank beforedigestion in the reactors. The result is that large amounts of biogas isbeing produced, i.e. typically 5 to 10 times more energy than containedin slurry.

[0438] The treatment in the GFE biogas and separation system furtherensures that the nutrients are re-circulated to agricultural land. Theenergy crops are digested in a separate reactor and the digested biomassis diverted to the stripper tank. In this tank the fibres not decomposedduring residence in the separate reactor will be hydrolysed and theammonia will be collected in the N-fraction. The N contained in energycrops can then be re-circulated to land and used in the production ofnew energy crops. About 1-3 kg N per tonnes silage can be reused.

[0439] The organic material according to the inveniton is preferablystripped for ammonia which in particular at thermopile temperatures isinhibitory to the biogas process (Hansen et al. 1998; Krylova et al.1997; Kayhanian 1994). The ammonia is stripped during the pretreatment,where the biomass is also being hydrolysed etc.

[0440] The process can preferably be split in a thermopile and amesopile component (Dugba and Zhang 1999; Han et al. 1997; Gosh et al.1985; Colleran et al. 1983). This gives rise to increased energy yieldsand working stability, among other thing because the biomass resideslonger in the bioreactors which allows the methane bacteria timedecompose the substrate. It should be noted that more energy for heatingis required as is a larger total reactor volume.

[0441] In addition to this two-step principle the plant shall make useof yet another reactor to preliminary digestion of poultry manure andsimilar N-containing biomasses. Also the energy crops shall be digestedin this reactor before further processing in the energy plant. Duringthis first digestion the main fraction of the readily available organicmatter is decomposed and the nitrogen released into solution in the formof ammonia. The nitrogen can now be stripped in the stripper tank andcollected in the N-fraction.

[0442] Digested beets, maize, clover grass etc. contain about 1 kg N pertonnes wet weight and it is therefore important that this N is collectedin the N-fraction. Poultry manure is even more N-rich and may also bedigested in the pre-digester before further digestion in the main biogasplant.

[0443] The stripping and hydrolysis ensures that also the recalcitrantfibres are made available to digestion as described under thepre-treatment. The following digestion in the main biogas plant ensuresa maximum gas yield.

[0444] The Fifth Aspect (Animal Welfare)

[0445] In a fifth preferred aspect the invention may be applied toensure optimal animal welfare and health when stabled in the animalhouses while at the same time reducing emissions of dust and gasses suchas ammonia. This is achieved by flushing or re-circulating reject waterthrough the animal houses with the purpose of cleaning and rinsingsties, floors, slats, manure canals etc. This reduces the emittingsurfaces where odour, ammonia and dust may be released to the in-doorair.

[0446] The system further allows the use of straw without increasing theemissions of dust and ammonia. The straw is a substantial welfarecomponent, in particular for pigs but also for other animals. Itprovides the animals with digging and occupational material andstructural fodder.

[0447] The reject water taken after the decanter centrifuge treatment(the third aspect) or possibly behind the first digestion (the firstaspect) is well suited as a means to flush the animal housings. Theflushing removes the straw and manure mixtures from the slats.

[0448] In further preferred aspects any combination of the coreinvention with the other aspects mentioned may be preferred. The firstaspect is preferably included in all combinations.

[0449] Accordingly, it will be clear from the above descriptions ofpreferred aspects and embodiments of the present invention that there isprovided herein:

[0450] A method for improved biogas production, said method comprisingthe steps of

[0451] i) stripping N including ammonia from organic materials includingmanures and slurries thereof, and optionally hydrolysing the organicmaterial,

[0452] ii) diverting the thus obtained organic material to a biogasfermentor, and

[0453] iii) obtaining biogas from the fermentation of the organicmaterial.

[0454] The above method may further comprise the step of separating thesolids resulting from the biogas fermentation in a separation stepinvolving a decanter centrifuge. Separate fractions of P and/or K,preferably in granulated form, are obtained from this separation.

[0455] The above method in another embodiment comprises the further stepof recirculating the liquids resulting from the biogas fermentation tostables or animal houses, optionally after a further purification step.

[0456] In another preferred embodiment, the step of N including ammoniastripping preferably occurs simultaneously with, or sequentially with,in any order, a step involving a thermal hydrolysis step and/or analkali hydrolysis step, wherein any one or both steps take place at anincreased temperature and/or an increased pressure as described hereinabove.

[0457] The above preferred embodiments thus in one embodiment solve theproblems associated with environmental contamination by undesirablemicrobial organisms, including Salmonella Typhimurium DT104, and/orprions associated with BSE that are present in organic materialsincluding manures and slurries thereof.

[0458] In another embodiment, the above described preferred embodimentssolve the problems associated with an attaining a sufficiently highhygienic standard in a stable or an animal house. This is achieved byreducing and/or eliminating undesirable microbial organisms and/orprions associated with BSE that are present in organic materialsincluding manures and slurries thereof.

[0459] In yet another embodiment, the above described preferredembodiments solve the problems associated with an excessive use ofexpensive water resources in a stable or an animal house. This problemis solved by re-using reject water obtained from the decanter centrifugeseparation step used for separating solids and liquids resulting i.e.from either pretreatment of organic material and/or N strippingincluding ammonia stripping and/or anaerobic fermentation leading tobiogas formation. At the same time, it is possible to reduce and/oreliminate the occurence of microbial microorganisms in the reject waterby further purification steps.

[0460] The present invention also provides cheep fertilisers ofcommercially acceptable standards. This is achieved by N-strippingincluding ammonia stripping and separation of P-containing granulatesand K-containing granulates by means of decanter centrifugationfollowing pretreatment, preferably including thermal and alkalihydrolysis.

[0461] In another aspect of the present invention there is provided amethod for reducing the number of viable microbial organisms and/or BSEprions present in an organic material, said method comprising the stepsof

[0462] i) providing an organic material comprising solid and/or liquidparts,

[0463] ii) reducing, in said organic material, the number of viablemicrobial organisms and/or BSE prions by subjecting the organic materialto

[0464] a) a lime pressure cooking step, and/or

[0465] b) a step wherein the organic material is heated at apredetermined temperature and/or subjected to a predetermined pressureand/or subjected to addition of base or acid, and/or

[0466] c) a step resulting in at least partial hydrolysis of the organicmaterial,

[0467] wherein said processing steps a), b) and c) can occursimultaneously, or sequentially in any order, and

[0468] iii) obtaining a processed organic material comprising at least areduced number of viable microbial organisms and/or BSE prions.

[0469] A wide variety of microbial organisms can be eliminated by themethods of the invention, including microbial organisms selected fromanimal microbial organisms, infectious microbial organisms, andparasitic pathogen microbial organisms, including any combinationthereof. Examples include, but is not limited to, bacteria such asCampylobacter, Salmonella, Yersinia, Ascaris, similar microbial andparasitic organisms, as well as virus, viroids and the like.

[0470] The lime cooking step may also serve to sterilize the organicmaterial in which case no viable microbial organisms survive this stepof processing. The lime preferably comprises or essentially consists ofCaO or Ca(OH)₂.

[0471] Preferably, any BSE prions or other prions present in the organicmaterial are also destroyed or eliminated by the sterilization process.When there is a reduction of microbial organisms and/or prions followingany one of the above-mentioned steps, the reduction be e.g. a 90%reduction, an 80% reduction, a 70% reduction, a 60% reduction, or areduction of preferably at least 50%.

[0472] It is preferred in one embodiment to improve the production ofbiogas by lime pressure cooking the organic material before the organicmaterial is subjected to a N stripping step. However, the lime pressurecooked organic material can also be fermented prior to being subjectedto a N stripping step.

[0473] When the organic material is of plant origin, it can preferablybe ensued before being diverting to N stripping. The ensued organicmaterial of plant origin can also be fermented prior to N stripping.Organic material to be ensilaged preferably comprises annual foddercrops such as beets, maize, clover grass, and wherein optionally the topof the plants is included.

[0474] Lime pressure cooking of the organic material is preferablyperformed at a temperature of from about 100° C. to about 250° C., undera pressure of 2-20 bar, with addition of lime sufficient to reach a pHvalue of from about 9 to about 12, and with an operation time of from atleast one 1 minute to preferably about less than 60 minutes.

[0475] The amount of added lime including CaO is preferably from about 2to about 80 g per kg dry matter, such as from about 5 to about 80 g perkg dry matter, such as from about 5 to about 60 g per kg dry matter,such as from about 10 to about 80 g per kg dry matter, such as fromabout 15 to about 80 g per kg dry matter, such as from about 20 to about80 g per kg dry matter, such as from about 40 to about 80 g per kg drymatter, such as from about 50 to about 80 g per kg dry matter, such asfrom about 60 to about 80 g per kg dry matter.

[0476] An example of operating conditions of the lime pressure cooker isa temperature in the interval of about 120° C. to about 220° C., apressure from about 2 bar to preferably about less than 18 bar, and anoperation time of from at least 1 minute to preferably less than 30minutes.

[0477] Another example of working conditions includes a temperature inthe interval of from about 180° C. to about 200° C., wherein thepressure is from about 10 bar to preferably less than 16 bar, whereinthe pH level is from about 10 to about 12, and wherein the operationtime is from about 5 minutes to about 10 minutes.

[0478] The above method can be following by a number of additionalsteps. In one embodiment, there is provided the further steps ofdiverting the processed organic material to a biogas fermenter,fermenting the processed organic material and obtaining a biogas.Another further step relates to supplementing an external environment,including an agricultural field, with the processed organic material.The supplementation of the external environment, including anagricultural field, can also be performed by using the residual materialresulting from the fermentation of the processed organic material.

[0479] Another further step is that of stripping nitrogen (N), includingammonia, from said organic material prior to diversion to a biogasfermentor of the organic material. This results in an increased andstable biogas production. This also allows the use of N-rich biomassesto be stripped and subsequently digested in the fermentors. Biogas isproduced from the fermentation of the organic material freed from atleast part of the N, including ammonia.

[0480] The stripped nitrogen (N) including ammonia is preferablyabsorbed in a column before optionally being stored in a tank. Whenbeing absorbed in a column, the stripped nitrogen (N) including ammoniais preferably absorbed in a column comprising water or an acidicsolution, preferably sulphuric acid, before optionally being stored in atank.

[0481] In one presently preferred embodiment there is provided a methodcomprising the steps of

[0482] i) eliminating, inactivating and/or reducing in said organicmaterial the number of viable microbial organisms and/or BSE prions bysubjecting the organic material to

[0483] a) a lime pressure cooking step, and/or

[0484] b) a step wherein the organic material is heated at apredetermined temperature and/or subjected to a predetermined pressureand/or subjected to addition of base or acid, and/or

[0485] c) a step resulting in at least partial hydrolysis of the organicmaterial,

[0486] wherein said processing steps a), b) and c) can occursimultaneously, or sequentially in any order,

[0487] ii) stripping N, including ammonia, from said processed organicmaterial,

[0488] iii) diverting the N stripped organic material to a biogasfermenter,

[0489] iv) fermenting the N stripped organic material, and

[0490] v) obtaining biogas and a fermented organic material at leasthaving a reduced number of viable microbial organisms and/or BSE prions.

[0491] It is much preferred that essentially no BSE prions are presentin the organic material resulting from the fermentation.

[0492] The step of stripping nitrogen (N), including ammonia, ispreferably performed by initially adding an amount of lime to theorganic material sufficient to increase the pH value to above 9 at atemperature of preferably above 40° C., such as a pH value of above 10at a temperature of preferably above 40° C., for example a pH value ofabove 11 at a temperature of preferably above 40° C., such as a pH valueof about 12 at a temperature of preferably above 40° C.

[0493] In preferred embodiments, the temperature is preferably above 50°C., such as above 55° C., for example above 60° C.

[0494] The operation time is in one embodiment from 2 to 15 days, suchas from 4 to 10 days, for example from 6 to 8 days. An example of oneset of process parameters is a pH level of from 8-12, a temperature offrom 70° C.-80° C., a liquid to gas ratio of less than 1:400, and anoperation time of about 7 days. The alkaline conditions can be generatedby adding any base. However, the pH is preferably increased by addingCaO or Ca(OH)₂.

[0495] The organic material can comprise solid and/or liquid parts suchas e.g. manures and slurries thereof, crop residues, silage crops,animal carcasses or fractions hereoff, slaughterhouse waste, meat andbone meal, including any combination thereof. In one embodiment, theorganic material comprises a maximum of 50% solid parts, for example amaximum of 40% solid parts; such as a maximum of 30% solid parts, forexample a maximum of 20% solid parts. The organic material can also bein a liquid state and comprise a maximum of 10% solid parts.

[0496] The organic material can further comprise straw, fibres orsawdust, and in one embodiment the organic material has a high contentof fibres, preferably more than 10% (w/w). The organic material can alsohave a high content of complex carbohydrates comprising cellulose,and/or hemicelluloses and/or lignin, such as preferably more than 10%(w/w). Lime pressure cooking cellulose containing organic materialresults in a disintegration of cellulose into small organic acids suchas formic acid, acetic acid, lactic acid, and the like.

[0497] The organic material can also comprise deep litter or manure fromanimals, especially from cattle, pigs and poultry holdings.Additionally, animal organic material can be used, such as e.g. animalcarcasses or fractions hereof, slaugtherhouse waste, meat and bone meal,blood plasma or any such produce originating from animals, risk- andno-risk material with respect to the potential presence of BSE-prions orother prions.

[0498] In one embodiment the organic material comprises or essentiallyconsists of solid parts of less than 10 cm in length, such as solidparts of less than 5 cm in length, for example solid parts of less than1 cm in length.

[0499] The organic material can preferably be macerated before beingtreated in the lime pressure cooker, preferably by using a screwconveyor equipped with a macerator, preferably one made of rust and acidproof steel. The conveyor conveys the organic material into the limecooker where the organic material is preferably heated by steaminjection, or by steam in a cape around the lime cooker, or anycombination thereof.

[0500] The organic material can also comprise proteins or similarorganic molecules comprising elements, including amino acids andcombinations thereof, constituting the BSE prions or other prions, andwherein said BSE prions or other prions are eliminated or destructeddirectly or rendered available for destruction by lime pressure cookingand/or subsequent fermentation, including anaerobic fermentation. Theorganic material of animal origin preferably has a high amount ofnitrogen (N), preferably more than 10%.

[0501] The organic material in the form of a liquid slurry can beobtained by the addition of water and/or water containing a lowconcentration of organic material, preferably less than 10% solid parts.The added water can be recycled water, water containing a lowconcentration of organic material obtained from the silage plant, and/orwater collected following cleaning of stables and/or cleaning ofanimals, and/or water obtained from the fermentation before the Nstripping process, and/or water obtained from one or more biogasproducing plants, and/or water obtained during concentration of Pfertilisers, and/or water obtained during concentration of Kfertilisers, and/or collected rain water.

[0502] It is in one embodiment particularly preferred that the water isreject water obtained from a biogas producing plant, or reject waterobtained during concentration of P fertilisers, or water obtained duringconcentration of K fertilisers, or collected rain water.

[0503] It is preferred that any or most of the urea and/or uric acidpresent in the organic material is converted into to ammonia, whereinthe ammonia is optionally collected following absorption to a collumn asdescribed elsewhere.

[0504] Additional steps besides lime pressure cooking is mesophilicand/or thermophilic fermentation. Accordingly, the organic materialwhich has been treated in the lime pressure cooker can subsequently bediverted into a plant for mesophilic and/or thermophilic fermentationbefore or after the organic material is subjected to N stripping.

[0505] Each fermentation is performed by a bacterial population capableof mesophilic or thermophilic fermentation, respectively. Thefermentation is in one embodiment an anaerobic fermentation.

[0506] The fermentation is preferably performed at a temperature of fromabout 15° C. to preferably less than about 65° C., such as at atemperature of from about 25° C. to preferably less than about 55° C.,for example at a temperature of from about 35° C. to preferably lessthan about 45° C.

[0507] The fermentation is preferably performed for a period of timefrom about 5 to preferably less than 15 days, such as for a period oftime from about 7 to preferably less than 10 days.

[0508] There is in one embodiment provided a method, wherein the biogasproduction is performed in one or more plants by a microbial organism,preferably a population of bacteria, and involves an anaerobicfermentation of the organic material. The bacteria preferably producemainly methane and a smaller fraction of carbon dioxide when fermentingthe organic material. The biogas production can be performed in one ormore plants, preferably by bacterial anaerobic fermentation of theorganic material.

[0509] In one embodiment, the biogas production is performed in twoplants by anaerobic bacterial fermentation of the organic material,initially by fermentation with thermophilic bacteria in a first plant,followed by diverting the thermophilicly fermented organic material to asecond plant, wherein fermentation with mesophilic bacteria takes place.

[0510] The thermophilic reaction conditions preferably include areaction temperature ranging from 45° C. to 75° C., such as a reactiontemperature ranging from 55° C. to 60° C.

[0511] The mesophilic reaction conditions preferably include a reactiontemperature ranging from 20° C. to 45° C., such as a reactiontemperature ranging from 30° C. to 35° C. The thermophilic reaction aswell as the mesophilic reaction is preferably performed for about 5 to15 days, such as for about 7 to 10 days.

[0512] Any potential foam formation can be reduced and/or eliminated bythe addition of polymers, and/or plant oils, and/or one or more salts,preferably plant oil in the form of rape oil. The salts preferablycomprise or essentially consist of CaO and/or Ca(OH)₂.

[0513] A desirable flocculation of substances and particles duringbiogas production is preferably achieved by the addition of calcium-ionscapable of forming calcium-bridges between organic and inorganicsubstances in solution or suspension, wherein said calcium-bridgesresulting in the formation of ‘flocks’ of particles. The addition ofcalcium-ions further results in the precipitation of orthophosphates,including dissolved (PO₄ ³⁻), which is preferably precipitated ascalcium phosphate Ca₃(PO₄)₂, wherein the precipitated calcium phosphatepreferably remains suspended in a slurry.

[0514] The obtained biogas can be diverted to a gas engine capable ofproducing heat and/or electricity. The heat can be used to heat the limepressure cooker and/or the fermentation plant and/or the N stripperreactor and/or the one or more biogas plant(s) and/or the animalhouse(s) and/or a human residence and/or heating water to be used in ahousehold or human residence. The electricity can be diverted and soldto a commercial net for distributing electricity. In one preferredembodiment, the remaining N stripped, sterilised and fermented organicmaterial is spread on agricultural fields.

[0515] In addition to i) reducing and/or eliminating undesirablemicrobial organisms, ii) improving the production of biogas, and iii)providing a highly usable N stripped, sterilised and fermented organicmaterial, the invention in another aspect pertains to a method forproducing N comprising fertilisers from organic materials comprising a Nsource, said production comprising the steps of i) collecting Nincluding ammonia stripped from the organic material in an N strippingstep, ii) absorbing said N including ammonia in water or an acidicsolution preferably comprising sulphuric acid, and iii) obtainingN-fertiliser which can be spread on agricultural land.

[0516] The invention in yet another aspect provides a method forproducing phosphor (P) comprising fertilisers from organic materialscomprising a P source, said production comprising the steps of i)diverting slurry from a biogas fermenter to a separator, ii) separatingthe fermented organic material as well as inorganic material into asolid and a mainly liquid fraction, iii) obtaining a mainly solidfraction comprising a part of the P, preferably in the form of calciumphosphate Ca₃(PO₄)₂, and organic phosphates suspended in the slurry,wherein said solid fraction is capable of being used as a P fertilisercapable of being spread on agricultural land when appropriate.

[0517] The separator for separating the fermented organic material aswell as inorganic material into a solid and a mainly liquid fraction ispreferably a decanter centrifuge. The mainly solid fraction comprising Pcan optionally be dried to produce a granulate comprising a Pfertiliser, e.g. by allowing the P-fraction to compost in a mile storeunder an air permeable sheet or cover.

[0518] The reject water obtained from the biogas production and theseparation from solid components can preferably be re-used in thefermentation of silage and/or in the lime pressure cooking processand/or in the N stripping process and/or in the biogas plant and/or incleaning of the stable and/or is spread on land and/or is lead to aconventional sewage treatment plant.

[0519] Accordingly, the method in another aspect provides for theproduction of substantially clean reject water, said productioncomprising the steps of i) obtaining from the separator, preferably adecanter centrifuge, a liquid fraction comprising reject water havingonly a very limited content of N and P, preferably less than 5% (w/v),such as less than 1% (w/v), for example less than 0.1% (w/v), such asless than 0.01% (w/v), and essentially no sources capable of spreadingzoonoses, veterinary vira, infectious bacteria, parasites or otherinfectious agents, including BSE prions and other prions. For someembodiments it is acceptable if the reject water contains less than 10%of the N and P originally obtained in the slurry.

[0520] In another aspect of the presnt invention there is provided amethod for producing potassium (K) comprising fertilisers from organicmaterials comprising a K source, said production comprising i) divertingthe liquid fraction from the first separation step (used in theseparation of P containing organic materials as described herein above)to a second separation step, ii) separating the remaining organic andinorganic composition from the liquid, iii) obtaining a solid fractioncomprising K, wherein said solid fraction is capable of being used as aK fertiliser capable of being spread on agricultural land whenappropriate.

[0521] The second separation step preferably comprises subjecting the Kcomprising fraction through a ceramic micro filter operating with anintermittent aeration and filtration of the reject water, whereinpreferably said aeration provides decomposition of the remaining organicmaterial and settling of inorganic flocks.

[0522] In another aspect there is provided a method for producing cleanreject water, wherein the obtained reject water is treated in an aerobictreatment system capable of eliminating and/or reducing the content of Nand P within the water and preferably also decomposing the remainingorganic material and smell components, obtaining reject wateressentially free from N and P, wherein said reject water is preferablycapable of being spread on agricultural land when appropriate, orre-circulated through an animal houses.

[0523] The above-mentioned aeration can be performed with atmosphericair during 2-4 weeks at a temperature of about 20° C. and a liquid-gasratio of about 1:2000. Any eliminated N can be collected and diverted tothe absorption column described herein elsewhere.

[0524] By being able to clean animal houses with the reject watertreated in this way, the invention also provides in yet another aspect amethod for improving the hygiene in an animal house or a stable foranimals, said improvement consisting in cleaning the stable with theobtained reject water. The cleaning involves cleaning and rinsing e.g.sties, floors, slats, manure canals, ceilings, ventilation canals,scrubbing exhaust air, etc., as well as reducing the emitting surfaceswhere odour, ammonia and dust may be released into the environment ofthe predetermined location including the stable.

[0525] The cleaning of the stables is in one embodiment preferablyperformed with reject water obtained following fermentation of energycrops or obtained following the fermentation to produce biogasseparation of solids and liquids or reject water obtained from a laterprocess in the system.

[0526] It is also possible according to this aspect of the invention toimprove animal welfare in a stable by utilising straw in the stable asit provides the animals with digging and occupational material andstructural fodder. It is preferred in one embodiment to divert the strawcomprising organic material from the stable to the lime pressure cookerandhydrolyse the organic material before further processing. Anotheroverall objective of the improvement of animal welfare in a stableresides in the possibility of being able to spray the animals in orderto reduce the number of microbial organisms as well as dust in the fursof the animals and simultaneously reduce the temperature of the animals.

[0527] In this way, there is provided a method integrating anaerobicfermentation of animal manures, energy crops and similar organicsubstrates, as well as refinement of nutrients held in the digestedbiomass to fertilizers of commercial quality, in combination withobtaining clean reject water.

[0528] The integrated method described herein above requires a system ofcomponents, or a selection of such components, as described herein inmore detail elsewhere.

[0529] In one aspect, the system comprises

[0530] i) a first device, preferably animal houses or stables forholding and/or breeding animals, preferably farm animals including cows,pigs, cattle, horses, goats, sheep and/or poultry, and the like, and/or

[0531] ii) a second device, preferably at least one pre-treatment plantfor pretreatment of organic material, said organic material preferablycomprises animal manure and/or animal slurry and/or plant parts, whereinsaid plant parts preferably comprise one or more of straw, crops, cropresidues, silage, energy crops, and optionally animal carcasses orfractions hereof, slaugtherhouse waste, meat and bone meal, blood plasmaor any such produce originating from animals, risk- and no-risk materialwith respect to the potential presence of BSE-prions or other prions,and/or

[0532] iii) a third device, preferably an energy plant generating animproved amount of energy from a biomass comprising organic material,

[0533] in which the first device comprises

[0534] a) a system for cleaning one or more of floors, slats, sties,manure canals, slurry canals, animals, and ventilation canals of ananimal house or a stable, said cleaning involving the use of cleaningwater, and/or

[0535] b) a system to transport the cleaning water, optionally in theform of a slurry comprising cleaning water and organic material, fromthe animal house or stable to the second device,

[0536] in which the second device comprises

[0537] a) a first pre-treatment tank, preferably a stripper tank for i)stripping N (nitrogen), including ammonia, from the slurry diverted fromthe first device to the second device, or ii) stripping N, includingammonia, from organic material diverted from an additional pretreatmenttank of the second devise, wherein the first pre-treatment tank canoptionally also be used for hydrolysing the organic material, and/or

[0538] b) a second pre-treatment tank, preferably a lime pressure cookerfor hydrolysing slurry comprising organic material diverted from thefirst device to the second device, wherein said hydrolysis results ineliminating, inactivating and/or reducing in number any viable microbialorganisms and/or pathogenic substances present in the slurry, or a partthereof, and/or

[0539] c) at least one tank, preferably a silage tank for generatingensued plant material comprising at least one or more of corn/maize,energy crops, beets, and crop residues, and/or

[0540] d) at least one second tank, preferably a pretreatment fermentingtank to ferment silage and/or lime pressure cooked organic material, inwhich the fermentation conditions are selected from mesophilicfermentation conditions and/or thermophilic fermentation conditions,

[0541] in which the third device comprises

[0542] a) at least one biogas fermenter to which slurry and/or organicmaterial can be diverted from the second device for fermenting theorganic material under either mesophilic fermentation conditions and/orthermophilic fermentation, said fermentation resulting in the productionof biogas comprising mainly methane and/or

[0543] b) at least one tank for collection of biogas, wherein the tankis optionally connected to an outlet for distribution of biogas, orconnected to a gas engine, and/or

[0544] c) at least one first separator, preferably a decanter centrifugein which the fermented material from the at least one biogas fermenteris separated into an essentially liquid fraction in the form of rejectwater, and an essentially solid fraction, wherein said solid fractioncomprises solid phosphor (P) comprising organic and inorganic material,and/or

[0545] d) at least one second separator, preferably a ceramicmicro-filter in which the reject water from the at least one firstseparator is further processed, preferably by aeration and filtration,wherein said processing results in removing at least some and preferablya majority of one or more of odour components, nitrogen (N) compoundsand potassium (K) compounds, wherein said separation further results inthe generation of reject water comprising a reduced amount of any one ormore of odour components, nitrogen (N) compounds and potassium (K)compounds as compared to the amount prior to separation.

[0546] The system preferably comprises pipe lines constituting a closedsystem preventing or leading to a reduction in emissions of any one ormore of dust, microbial organisms, ammonia, air, liquid or any otherconstituent within the system.

[0547] Liquid fractions or reject water from one or more of the at leastone silage tank, the at least one pre-treatment fermenting tank, the atleast one biogas fermentor, the at least one first separator and the atleast one second separator is preferably re-used for cleaning of theanimal house or the stable.

[0548] The liquid fractions or reject water from any one or more of theat least one silage tank, the at least one pretreatment fermenting tank,the at least one biogas fermentor, the at least one first separator andthe at least one second separator is preferably re-used in any step ofthe slurry separation and biogas production system to maintain theorganic material in a proper fluid condition.

[0549] The system makes it possible to add lime, including CaO and/orCa(OH)₂, to the organic material before said organic material enters thestripper tank for stripping N including ammonia, preferably by adding anamount of lime sufficient to generate a pH value of from about 10 toabout 12, optionally in combination with a heating step and an aerationof the slurry including the organic material.

[0550] The organic material preferably remains in the stripper tank ofthe system for a period of 5 to 10 days, such as 7 days. The temperatureinside the stripper tank is preferably between 60° C. and 80° C. Anamount of from about 30 and 60 gram Ca(OH)₂ per kg dry matter in theorganic material is preferably added to the organic material in thestripper tank or before said organic material enters the stripper tank.

[0551] The system facilitates colloction of stripped N including ammoniafrom the stripper tank and diversion of said stripped N to a column inwhich N including ammonia is absorbed in water or an acid solutionpreferably comprising sulphuric acid, and optionally also storing theabsorbed ammonia in a tank. The N absorbed in water or an acid solutionin this way is preferably used as a fertiliser.

[0552] The lime pressure cooker of the system is preferably an apparatuswhich is initially capable of cutting the organic material into segmentsand subsequently capable of diverting the segmented organic material toa chamber wherein said segmented organic material is heated andsimultaneously exposed to a high pressure due to the elevatedtemperature. The organic material to be treated in the lime pressurecooker is added an amount of lime, including CaO and/or Ca(OH)₂, priorto or after entry into the lime pressure cooker.

[0553] Preferably CaO is added to the lime pressure cooker in an amountof from 5-10 g per kg dry matter in the organic material. The systemoperates at a temperature of between 100° C. and 220° C., such as e.g.180° C. to 200° C. The temperature is aligned according to the organicmaterial to be treated, a higher temperature is chosen the higher thecontent of cellulose, hemicellulose and lignin is in the organicmaterial, or a higher temperature is chosen according to the risk ofinfectious microbial organism or pathogenic compounds including BSEprions in the organic material.

[0554] The pressure is between preferably between from 2 to preferablyless than 16 bar, such as from 4 to preferably less than 16 bar, forexample from 6 to preferably less than 16 bar, such as from 10 topreferably less than 16 bar. The system operates at the elevatedtemperature for about 5 to 10 minutes, but longer treatment times canalso be used.

[0555] N including ammonia stripped in the lime pressure cooker ispreferably collected and diverted to a column and absorbed as describedherein elsewhere.

[0556] The system in one embodiment facilitates diversion of silage suchas e.g. maize, energy crops, beets, and/or crop residues, to amesophilic or thermophilic fermentation tank, before the material isfurther diverted to the stripper tank.

[0557] The system can also facilitate diversion of lime pressure cookedorganic material to a mesophilic or thermophilic fermentation tank,before the material is diverted to the stripper tank.

[0558] The system also facilitates the optimization of the fermentationof the organic material and the production of biogas by providing apre-treatment plant comprising facilities for stripping N includingammonia and/or performing alkaline hydrolysis under predeterminedprocess parameters, including pH level, temperature, aeration, duration,foam inhibition and flocculation of suspended material.

[0559] The system in another embodiment ensures optimised conditions forthe population of microbial organisms contained in the biogas producingfermenters. This is achieved by e.g. diverting sterilised or sanitisedslurry from the stripper tank to at least a first biogas fermenter,wherein said sterilised or sanitised slurry do not inhibit or harm thepopulation of biogas producing microbial organism in the fermenter. Inparticular, organic material from which N including ammonia is stripped,can be diverted to a biogas reactor in which the fermentation conditionssupports a mesophilic fermentation. Once the organic material has beensubjected to a mesophilic fermentation, the organic material ispreferably diverted to another biogas reactor of the system, in whichthe fermentation conditions are capable of supporting a thermophilicfermentation.

[0560] The thermophilic reaction conditions include a reactiontemperature ranging from about 45° C. to 75° C., such as a reactiontemperature ranging from about 55° C. to 60° C. The mesophilic reactionconditions include a reaction temperature ranging from about 20° C. to45° C., including a reaction temperature ranging from about 30° C. to35° C.

[0561] The system allows for both the thermophilic reaction and themesophilic reaction to occur for about or at least 5-15 days, such asfor about or at least 7-10 days, preferably at least 7 days.

[0562] The system comprises devices capable of preventing foamformation, wherein said devices are capable of adding e.g. polymers,and/or plant oils, including rape oil, and/or different salts, includingsalts comprising CaO and/or Ca(OH)₂.

[0563] The system makes it possible to reuse at least part of thefermented organic material from the biogas reactors in that samereactor, wherein said fermented organic material functions as aninoculum of the population of microbial organism performing thefermentation.

[0564] The system makes it possible in one embodiment to divert a slurryincluding a liquid comprising solid parts, to a first separator forseparating the solid materials including a limited fraction of theliquid from the main part of the liquid fraction. Said mainly solidfraction comprises organic and inorganic material including P (phosphor)and compounds hereof. Said mainly solid fraction can be further driedand comprises a fertiliser. The first separator of the system ispreferably a decanter centrifuge.

[0565] The system also allows reject water from the first separator tobe treated in a second separator, said second separator comprising aceramic micro-filters in which the reject water from the first separatoris further processed by aeration and filtration, optionally removing anyresidual odour components, any residual nitrogen compounds and/or anycomponents containing K (potassium), leaving an essentially clean rejectwater comprising essentially none of said residual components.

[0566] The system makes it possible to divert the reject water from thethermophilic biogas reactor or from the first and/or second separator toan agricultural field, to a waste water treatment plant, or a purifyingplant, or a biological treatment plant for further purification ifrequired.

[0567] The system or the methods of the present invention can be usedto:

[0568] eliminate or decline the emission to the environment of dust,microbial organisms, ammonia, contaminated air, liquid or any otherconstitution within the system, especially from animal houses.

[0569] improve the utilisation of the energy contained in a biomassincluding organic material.

[0570] improve the production of biogas comprising methane gas andmethane-bearing gas. Said gas may be stored in a tank locally and/or canbe diverted to a commercial net of distributing gas.

[0571] obtain separate fractions of N (nitrogen), P (phosphor) andpotentially K (potassium) from organic materials. Said fractions are ofcommercial value and can be utilised as fertilisers to fertiliseagricultural and horticultural crops.

[0572] obtain an improved animal welfare and improved hygiene in animalstables and in accordance to output from said animal stables. Saidoutput comprising manure, slurry and animals to be slaughtered. Theclean animals reduces the risk of infection of meat when the animals areslaughtered.

[0573] obtain a proceedure for rendering animal carcases or fractionshereof, meat and bone meal or any other produce from animals availablefor disposing off to agricultural land in the form of refinedfertilizers and thus to benefit from micro- and macro- nutrients in theanimal produce in the agricultural or horticultural plant production.

1. A method for reducing the number of viable microbial organisms and/orBSE prions present in an organic material, said method comprising thesteps of i) providing an organic material comprising solid and/or liquidparts, ii) reducing, in said organic material, the number of viablemicrobial organisms and/or BSE prions by subjecting the organic materialto a) a lime pressure cooking step, and/or b) a step wherein the organicmaterial is heated at a predetermined temperature and/or subjected to apredetermined pressure and/or subjected to addition of base or acid,and/or c) a step resulting in at least partial hydrolysis of the organicmaterial, wherein said processing steps a), b) and c) can occursimultaneously, or sequentially in any order, and iii) obtaining aprocessed organic material comprising at least a reduced number ofviable microbial organisms and/or BSE prions.
 2. The method of claim 1comprising the further steps of diverting the processed organic materialto a biogas fermenter, fermenting the processed organic material andobtaining a biogas.
 3. The method of claim 1 comprising the further stepof supplementing an external environment, including an agriculturalfield, with the processed organic material.
 4. The method of claim 2comprising the further step of supplementing an external environment,including an agricultural field, with the residual material resultingfrom the fermentation of the processed organic material.
 5. The methodof claim 2 comprising the further steps of stripping nitrogen (N),including ammonia, from said organic material prior to the diversion toa biogas fermentor of the organic material, and obtaining biogas fromthe fermentation of the organic material freed from at least part of theN, including ammonia.
 6. The method of any of claims 1 to 5, whereinsaid microbial organisms are selected from animal microbial organisms,infectious microbial organisms, and parasitic pathogen microbialorganisms, including any combination thereof.
 7. The method of any ofclaims 1 and 5, wherein said organic material comprising solid and/orliquid parts is selected from manures and slurries thereof, cropresidues, silage crops, animal carcasses or fractions hereoff,slaughterhouse waste, meat and bone meal, including any combinationthereof.
 8. The method of claim 5, wherein the biogas production isfurther improved by lime pressure cooking said organic material beforethe organic material is subjected to a N stripping step.
 9. The methodof claim 8, wherein the lime pressure cooked organic material isfermented prior to being subjected to a N stripping step.
 10. The methodof claim 5, wherein the organic material of plant origin is ensiledbefore it is diverting to a N stripping step.
 11. The method of claim10, wherein the ensiled organic material of plant origin is fermentedprior to N stripping.
 12. The method of claim 1 comprising the steps ofi) eliminating, inactivating and/or reducing in said organic materialthe number of viable microbial organisms and/or BSE prions by subjectingthe organic material to a) a lime pressure cooking step, and/or b) astep wherein the organic material is heated at a predeterminedtemperature and/or subjected to a predetermined pressure and/orsubjected to addition of base or acid, and/or c) a step resulting in atleast partial hydrolysis of the organic material, wherein saidprocessing steps a), b) and c) can occur simultaneously, or sequentiallyin any order, ii) stripping N, including ammonia, from said processedorganic material, iii) diverting the N stripped organic material to abiogas fermenter, iv) fermenting the N stripped organic material, and v)obtaining biogas and a fermented organic material at least having areduced number of viable microbial organisms and/or BSE prions.
 13. Themethod of claim 12, wherein essentially no BSE prions are present in theorganic material resulting from the fermentation.
 14. The method ofclaim 5, wherein the step of stripping nitrogen (N), including ammonia,is performed by initially adding an amount of lime to the organicmaterial to increase the pH value to above 9 at a temperature ofpreferably above 40° C.
 15. The method of claim 14, wherein the pH valueis above
 10. 16. The method of claim 14, wherein the pH value is above11.
 17. The method of claim 14, wherein the temperature is above 50° C.18. The method of claim 14, wherein the temperature is above 60° C. 19.The method of claim 14, wherein the operation time is from 2 to 15 days.20. The method of claim 14, wherein the operation time is from 4 to 10days.
 21. The method of claim 14, wherein the operation time is from 6to 8 days.
 22. The method of claim 14, wherein the pH level is 8-12, thetemperature 70° C.-80° C., the liquid to gas ratio is less than 1:400,and the operation time is about 7 days.
 23. The method of claim 14,wherein the organic material comprises a maximum of 50% solid parts. 24.The method of claim 14, wherein the organic material comprises a maximumof 40% solid parts.
 25. The method of claim 14, wherein the organicmaterial comprises a maximum of 30% solid parts.
 26. The method of claim14, wherein the organic material comprises a maximum of 20% solid parts.27. The method of claim 14, wherein the organic material is in an fluidcondition comprising a maximum of 10% solid parts.
 28. The method ofclaim 14, wherein the organic material is a liquid slurry obtained bythe addition of water and/or water containing a low concentration oforganic material, preferably less than 10% solid parts.
 29. The methodof claim 28, wherein the added water includes water containing a lowconcentration of organic material obtained from the silage plant, and/orwater collected following cleaning of stables and/or cleaning ofanimals, and/or water obtained from the fermentation before the Nstripping process, and/or water obtained from one or more biogasproducing plants, and/or water obtained during concentration of Pfertilisers, and/or water obtained during concentration of Kfertilisers, and/or collected rain water.
 30. The method of claim 28,wherein the added water is reject water obtained from a biogas producingplant.
 31. The method of claim 28, wherein the added water is rejectwater obtained during concentration of P fertilisers.
 32. The method ofclaim 28, wherein the added water is water obtained during concentrationof K fertilisers.
 33. The method of claim 28, wherein the added water iscollected rain water.
 34. The method of claim 14, wherein the pH isincreased by adding CaO
 35. The method of claim 14, wherein the pH isincreased by adding Ca(OH)₂.
 36. The method of claim 14, wherein thestripped nitrogen (N) including ammonia is absorbed in a column beforeoptionally being stored in a tank.
 37. The method of claim 14, whereinthe stripped nitrogen (N) including ammonia is absorbed in a columncomprising water or an acidic solution, preferably sulphuric acid,before optionally being stored in a tank.
 38. The method of any ofclaims 1-14, wherein the step of lime pressure cooking the organicmaterial is performed at a temperature of from about 100° C. to about250° C., under a pressure of 2-20 bar, with addition of lime sufficientto reach a pH value of from about 9 to about 12, and with an operationtime of from at least one 1 minute to preferably about less than 60minutes.
 39. The method of claim 38, wherein the organic materialfurther comprises deep litter or manure from animals, especially fromcattle, pigs and poultry holdings.
 40. The method of claim 38, whereinthe organic material further comprises animal carcasses or fractionshereof, slaugtherhouse waste, meat and bone meal, blood plasma or anysuch produce originating from animals, risk- and no-risk material withrespect to the potential presence of BSE-prions or other prions.
 41. Themethod of claim 38, wherein the organic material further comprisesproteins or similar organic molecules comprising elements, includingamino acids and combinations thereof, constituting the BSE prion orother prions, and wherein said BSE prions or other prions are eliminatedor destructed directly or rendered available for destruction in theanaerobic fermentation
 42. The method of claim 38, wherein the organicmaterial further comprises straw, fibres or sawdust.
 43. The method ofclaim 38, wherein the organic material has a high content of fibres,preferably more than 10% (w/w).
 44. The method of claim 38, wherein theorganic material has a high content of complex carbohydrates comprisingcellulose, and/or hemicelluloses and/or lignin, preferably more than 10%(w/w).
 45. The method of claim 38, wherein the organic materialcomprising cellulose, following lime pressure cooking, disintegratesinto small organic acids such as formic acid, acetic acid, lactic acid,and the like.
 46. The method of claim 38, wherein any urea or uric acidpresent in the organic material is converted into to ammonia, andwherein the ammonia is optionally collected as described in the methodof any of claims 36 and
 37. 47. The method of claim 38, wherein the limecomprises or essentially consists of CaO or Ca(OH)2.
 48. The method ofclaim 47, wherein the amount of added CaO is from about 2 to about 80 gper kg dry matter.
 49. The method of claim 47, wherein the amount ofadded CaO is from about 5 to about 60 g per kg dry matter.
 50. Themethod of claim 38, wherein the temperature is in the interval of about120° C. to about 220° C., wherein the pressure is from about 2 bar topreferably about less than 18 bar, and wherein the operation time isfrom at least 1 minute to preferably less than 30 minutes.
 51. Themethod of claim 38, wherein the temperature is in the interval of about180° C. to about 200° C., wherein the pressure is from about 10 bar topreferably less than 16 bar, wherein the pH level is from about 10 toabout 12, and wherein the operation time is from about 5 minutes toabout 10 minutes.
 52. The method of claim 38, wherein the organicmaterial comprises or essentially consists of solid parts of less than10 cm in length.
 53. The method of claim 38, wherein the organicmaterial comprises or essentially consists of solid parts of less than 5cm in length.
 54. The method of claim 38, wherein the organic materialcomprises or essentially consists of solid parts of less than 1 cm inlength.
 55. The method of any of claims 38 and 52-54, wherein theorganic material is macerated before being treated in the lime cooker.56. The method of claim 55, wherein a screw conveyor equipped with amacerator, preferably made of rust and acid proof steel, conveys theorganic material into the lime cooker where the organic material isheated by steam injection, or by steam in a cape around the lime cooker,or any combination thereof.
 57. The method of claim 38, wherein theorganic material treated in the lime pressure cooker is subsequentlydiverted into a plant for mesophilic and/or thermophilic fermentationbefore the organic material is subjected to N stripping.
 58. The methodof claim 57, wherein the fermentation is performed by a bacterialpopulation.
 59. The method of claim 57, wherein the fermentation is ananaerobic fermentation.
 60. The method of claim 57, wherein the organicmaterial of animal origin has a high amount of nitrogen (N), preferablymore than 10%.
 61. The method of claim 57, wherein the fermentation isperformed at a temperature of from about 15° C. to preferably less thanabout 65° C.
 62. The method of claim 57, wherein the fermentation isperformed at a temperature of from about 25° C. to preferably less thanabout 55° C.
 63. The method of claim 57, wherein the fermentation isperformed at a temperature of from about 35° C. to preferably less thanabout 45° C.
 64. The method of claim 57, wherein the fermentation isperformed for a period of time from about 5 to preferably less than 15days.
 65. The method of claim 57, wherein the fermentation is performedfor a period of time from about 7 to preferably less than 10 days. 66.The method of claim 10, wherein the organic material to be ensilagedcomprises annual fodder crops such as beets, maize, clover grass, andwherein optionally the top of the plants is included.
 67. A method ofany of the claims 1-14, wherein the biogas production is performed inone or more plants by a microbial organism, preferably a bacteria, andinvolves an anaerobic fermentation of the organic material.
 68. Themethod of claim 67, wherein the bacteria produce mainly methane and asmaller fraction of carbon dioxide when fermenting the organic material.69. The method of claim 67, wherein the biogas production is performedin one or more plants by bacterial anaerobic fermentation of the organicmaterial.
 70. The method of claim 67, wherein the biogas production isperformed in two plants by anaerobic bacterial fermentation of theorganic material, initially by fermentation with thermophilic bacteriain a first plant, followed by diverting the thermophilicly fermentedorganic material to a second plant, wherein fermentation with mesophilicbacteria takes place.
 71. The method of claim 70, wherein thethermophilic reaction conditions include a reaction temperature rangingfrom 45° C. to 75° C.
 72. The method of claim 70, wherein thethermophilic reaction conditions include a reaction temperature rangingfrom 55° C. to 60° C.
 73. The method of claim 70, wherein the mesophilicreaction conditions include a reaction temperature ranging from 20° C.to 45° C.
 74. The method of claim 70, wherein the mesophilic reactionconditions include a reaction temperature ranging from 30° C. to 35° C.75. The method of claim 70, wherein the thermophilic reaction isperformed for about 5 to 15 days.
 76. The method of claim 70, whereinthe thermophilic reaction is performed for about 7 to 10 days.
 77. Themethod of claim 70, wherein the mesophilic reaction is performed forabout 5 to 15 days.
 78. The method of claim 70, wherein the mesophilicreaction is performed for about 7 to 10 days.
 79. The method of claim70, wherein any potential foam formation is reduced and/or eliminated bythe addition of polymers, and/or plant oils, and/or one or more salts.80. The method of claim 79, wherein the plant oil is rape oil.
 81. Themethod of claim 79, wherein the salts comprises or essentially consistsof CaO and/or Ca(OH)₂.
 82. The method of claim 67, wherein a desirableflocculation of substances and particles during biogas production isachieved by the addition of calcium-ions capable of formingcalcium-bridges between organic and inorganic substances in solution orsuspension, said calcium-bridges resulting in the formation of ‘flocks’of particles.
 83. The method of claim 82, wherein addition ofcalcium-ions further results in the precipitation of orthophosphates,including dissolved (PO₄ ³⁻), which is preferably precipitated ascalcium phosphate Ca₃(PO₄)₂, wherein the precipitated calcium phosphatepreferably remains suspended in a slurry.
 84. The method of claim 67,wherein the obtained biogas is diverted to a gas engine capable ofproducing heat and/or electricity.
 85. The method of claim 84, whereinsaid heat is used to heat the lime pressure cooker and/or thefermentation plant and/or the N stripper reactor and/or the one or morebiogas plant(s) and/or the animal house(s) and/or a human residenceand/or heating water to be used in a household or human residence. 86.The method of claim 84, wherein said electricity is diverted and sold toa commercial net for distributing electricity.
 87. The method of claim67, wherein the N stripped, sterilised and fermented organic material isspread on agricultural fields.
 88. The method of claim 1 to 14 whereinthe microbial organisms include bacteria such as Campylobacter,Salmonella, Yersinia, Ascaris, similar microbial and parasiticorganisms, as well as virus, viroids and the like.
 89. The method of anyof claims 5 to 14, further comprising the step of producing N comprisingfertilisers from organic materials comprising a N source, saidproduction comprising the steps of i) collecting N including ammoniastripped from the organic material in an N stripping step, ii) absorbingsaid N including ammonia in water or an acidic solution preferablycomprising sulphuric acid, and iii) obtaining N-fertiliser which can bespread on agricultural land.
 90. The method of claim 5 to 14 furthercomprising the step of producing phosphor (P) comprising fertilisersfrom organic materials comprising a P source, said production comprisingthe steps of i) diverting slurry from the biogas fermenter to aseparator, ii) separating the fermented organic material as well asinorganic material into a solid and a mainly liquid fraction, iii)obtaining a mainly solid fraction comprising a part of the P, preferablyin the form of calcium phosphate Ca₃(PO₄)₂ and organic phosphatessuspended in the slurry, wherein said solid fraction is capable of beingused as a P fertiliser capable of being spread on agricultural land whenappropriate.
 91. The method of claim 90, wherein the separator is adecanter centrifuge.
 92. The method of claim 90, wherein the mainlysolid fraction comprising P is dried to produce a granulate comprising aP fertiliser, optionally by allowing the P-fraction to compost in a milestore under an air permeable sheet or cover.
 93. The method of claim 5to 14, wherein reject water obtained from the biogas production and theseparation from solid components is re-used in the fermentation ofsilage and/or in the lime pressure cooking process and/or in the Nstripping process and/or in the biogas plant and/or in cleaning of thestable and/or is spread on land and/or is lead to a conventional sewagetreatment plant.
 94. The method of claim 5 to 14, further comprising thestep of producing substantially clean reject water, said productioncomprising the steps of i) obtaining from the separator the liquidfraction comprising reject water having only a very limited content of Nand P, and essentially no sources capable of spreading zoonoses,veterinary vira, infectious bacteria, parasites or other infectiousagents, including BSE prions and other prions.
 95. The method of claim94, wherein the reject water contains less than 10% of the N and Poriginally obtained in the slurry.
 96. The method of claim 5 to 14further comprising the step of producing potassium (K) comprisingfertilisers from organic materials comprising a K source, saidproduction comprising i) diverting the liquid fraction from the firstseparation step to a second separation step, ii) separating theremaining organic and inorganic composition from the liquid, iii)obtaining a solid fraction comprising K, wherein said solid fraction iscapable of being used as a K fertiliser capable of being spread onagricultural land when appropriate.
 97. The method of claim 96, whereinthe second separation step comprises subjecting the K comprisingfraction through a ceramic micro filter operating with an intermittentaeration and filtration of the reject water, wherein preferably saidaeration provides decomposition of the remaining organic material andsettling of inorganic flocks.
 98. A method of claim 94 furthercomprising the step of producing clean reject water, wherein theobtained reject water is treated in an aerobic treatment system capableof eliminating and/or reducing the content of N and P within the waterand preferably also decomposing the remaining organic material and smellcomponents, obtaining reject water essentially free from N and P,wherein said reject water is preferably capable of being spread onagricultural land when appropriate, or re-circulated through an animalhouses.
 99. The method of claim 98, wherein the aeration is performedwith atmospheric air during 2-4 weeks.
 100. The method of claim 98,wherein the temperature is kept at about 20° C.
 101. The method of claim98, wherein the liquid-gas ratio is about 1:2000.
 102. The method ofclaim 98, wherein the eliminated N is collected and diverted to theabsorption column according to claim 36 and
 37. 103. A method of claim94 further comprising the step of improving the hygiene in a stable foranimals, said improvement consisting in cleaning the stable with theobtained reject water.
 104. The method of claim 103, wherein thecleaning of the stable comprises cleaning and rinsing sties, floors,slats, manure canals, ceilings, ventilation canals, scrubbing exhaustair, etc., reducing the emitting surfaces where odour, ammonia and dustmay be released into the environment of the predetermined locationincluding the stable.
 105. The method of claim 103, wherein the cleaningof the stable is performed with reject water obtained followingfermentation of energy crops or obtained following the fermentation toproduce biogas separation of solids and liquids or reject water obtainedfrom a later process in the system.
 106. A method of claim 103 furthercomprising a method to improve animal welfare in a stable utilisingstraw in the stable, it provides the animals with digging andoccupational material and structural fodder, and diverting said strawcomprising organic material from the stable to the lime pressurecooking, hydrolysing the organic material before further processing.107. A method of claim 103 further comprising a method to improve animalwelfare in a stable comprising spraying the animals to reduce the numberof microbial organisms as well as dust on the surface of the animals andsimultaneously reducing the temperature of the animals.
 108. The methodof any of the preceding claims further comprising a method wherein theintegrated system comprising anaerobic fermentation of animal manures,energy crops and similar organic substrates, as well as refinement ofnutrients held in the digested biomass to fertilizers of commercialquality, in combination with obtaining clean reject water, is situatedat a farm for local processing of the organic material.
 109. A systemcomprising i) a first device, preferably animal houses or stables forholding and/or breeding animals, preferably farm animals including cows,pigs, cattle, horses, goats, sheep and/or poultry, and the like, and/orii) a second device, preferably at least one pre-treatment plant forpretreatment of organic material, said organic material preferablycomprises animal manure and/or animal slurry and/or plant parts, whereinsaid plant parts preferably comprise one or more of straw, crops, cropresidues, silage, energy crops, and optionally animal carcasses orfractions hereof, slaugtherhouse waste, meat and bone meal, blood plasmaor any such produce originating from animals, risk- and no-risk materialwith respect to the potential presence of BSE-prions or other prions,and/or iii) a third device, preferably an energy plant generating animproved amount of energy from a biomass comprising organic material, inwhich the first device comprises a) a system for cleaning one or more offloors, slats, sties, manure canals, slurry canals, animals, andventilation canals of an animal house or a stable, said cleaninginvolving the use of cleaning water, and/or b) a system to transport thecleaning water, optionally in the form of a slurry comprising cleaningwater and organic material, from the animal house or stable to thesecond device, in which the second device comprises a) a firstpre-treatment tank, preferably a stripper tank for i) stripping N(nitrogen), including ammonia, from the slurry diverted from the firstdevice to the second device, or ii) stripping N, including ammonia, fromorganic material diverted from an additional pre-treatment tank of thesecond devise, wherein the first pre-treatment tank can optionally alsobe used for hydrolysing the organic material, and/or b) a secondpre-treatment tank, preferably a lime pressure cooker for hydrolysingslurry comprising organic material diverted from the first device to thesecond device, wherein said hydrolysis results in eliminating,inactivating and/or reducing in number any viable microbial organismsand/or pathogenic substances present in the slurry, or a part thereof,and/or c) at least one tank, preferably a silage tank for generatingensiled plant material comprising at least one or more of corn/maize,energy crops, beets, and crop residues, and/or d) at least one secondtank, preferably a pre-treatment fermenting tank to ferment silageand/or lime pressure cooked organic material, in which the fermentationconditions are selected from mesophilic fermentation conditions and/orthermophilic fermentation conditions, in which the third devicecomprises a) at least one biogas fermenter to which slurry and/ororganic material can be diverted from the second device for fermentingthe organic material under either mesophilic fermentation conditionsand/or thermophilic fermentation, said fermentation resulting in theproduction of biogas comprising mainly methane and/or b) at least onetank for collection of biogas, wherein the tank is optionally connectedto an outlet for distribution of biogas, or connected to a gas engine,and/or c) at least one first separator, preferably a decanter centrifugein which the fermented material from the at least one biogas fermenteris separated into an essentially liquid fraction in the form of rejectwater, and an essentially solid fraction, wherein said solid fractioncomprises solid phosphor (P) comprising organic and inorganic material,and/or d) at least one second separator, preferably a ceramicmicro-filter in which the reject water from the at least one firstseparator is further processed, preferably by aeration and filtration,wherein said processing results in removing at least some and preferablya majority of one or more of odour components, nitrogen (N) compoundsand potassium (K) compounds, wherein said separation further results inthe generation of reject water comprising a reduced amount of any one ormore of odour components, nitrogen (N) compounds and potassium (K)compounds as compared to the amount prior to separation.
 110. A systemaccording to claim 109, wherein liquid fractions or reject water fromone or more of the at least one silage tank, the at least onepretreatment fermenting tank, the at least one biogas fermentor, the atleast one first separator and the at least one second separator isre-used for cleaning of the animal house or the stable.
 111. A systemaccording to claim 109, wherein the system comprises pipe linesconstituting a closed system preventing or leading to a reduction inemissions of any one or more of dust, microbial organisms, ammonia, air,liquid or any other constituent within the system.
 112. A systemaccording to claim 109, wherein liquid fractions or reject water fromany one or more of the at least one silage tank, the at least onepretreatment fermenting tank, the at least one biogas fermentor, the atleast one first separator and the at least one second separator isre-used in any step of the slurry separation and biogas productionsystem to maintain the organic material in a proper fluid condition.113. A system according to claim 109, wherein lime including CaO and/orCa(OH)₂ is added to the organic material before said organic materialenters the stripper tank for stripping N including ammonia, preferablyby adding an amount of lime sufficient to generate a pH value of fromabout 10 to about 12, optionally in combination with a heating step andan aeration of the slurry including the organic material.
 114. A systemaccording to claim 109, wherein the organic material remains in thestripper tank for a period of 5 to 10 days, optionally 7 days.
 115. Asystem according to claim 109, wherein the temperature inside thestripper tank is between 60° C. and 80° C.
 116. A system according toclaim 109, wherein an amount of between 30 and 60 gram Ca(OH)₂ per kgdry matter in the organic material is added to the organic material inthe stripper tank or before said organic material enters the strippertank.
 117. A system according to claim 109, wherein the stripped Nincluding ammonia is collected from the stripper tank and diverted to acolumn in which ammonia is absorbed in water or an acid solutionpreferably comprising sulphuric acid, and optionally storing theabsorbed ammonia in a tank.
 118. A system according to claim 109,wherein the N absorbed in an acid solution is utilised as a fertiliser.119. A system according to claim 109, wherein the lime pressure cookeris an apparatus which first cuts the organic material into segments andsecond diverts the segmented organic material to a chamber wherein saidsegmented organic material is heated and simultaneously exposed to ahigh pressure due to the elevated temperature.
 120. A system accordingto claim 109, wherein the organic material to be treated in the limepressure cooker is added an amount of lime.
 121. A system according toclaim 109, wherein the organic material to be treated in the limepressure cooker is added lime in the form of CaO or Ca(OH)₂.
 122. Asystem according to claim 109, wherein the organic material to betreated in the lime pressure cooker is added CaO.
 123. A systemaccording to claim 109, wherein the organic material to be treated inthe lime pressure cooker is added CaO of 5-10 g per kg dry matter in theorganic material.
 124. A system according to claim 109, wherein thetemperature of the organic material in the lime pressure cooker isbetween 100° C. and 220° C. Said temperature is aligned according to theorganic material to be treated, a higher temperature is chosen thehigher the content of cellulose, hemicellulose and lignin is in theorganic material, or a higher temperature is chosen according to therisk of infectious microbial organism or pathogenic compounds includingBSE prions in the organic material.
 125. A system according to claim109, wherein the temperature of the organic material in the limepressure cooker is between 180° C. and 200° C.
 126. A system accordingto claim 109, wherein the pressure of the organic material in the limepressure cooker is between 10 and 16 bar.
 127. A system according toclaim 109, wherein the organic material in the lime pressure cooker istreated with the elevated temperature for 5 to 10 minutes.
 128. A systemaccording to claim 109, wherein N including ammonia stripped in the limepressure cooker is collected and diverted to a column and absorbed asdescribed in claim
 117. 129. A system according to claim 109, whereinsilage of, but not limited to, maize, energy crops, beets, and/or cropresidues, is diverted to a mesophilic or thermophilic fermentation tank,before further diverted to the stripper tank.
 130. A system according toclaim 109, wherein lime pressure cooked organic material is diverted toa mesophilic or thermophilic fermentation tank, before further divertedto the stripper tank.
 131. A system according to claim 109, wherein thefermentation of the organic material and the production of biogas isoptimised by pretreatment comprising stripping N including ammonia andalkaline hydrolysis at conditions including a proper pH level,temperature, aeration, duration, foam inhibition and flocculation ofsuspended material.
 132. A system according to claim 109, wherein themicrobial organism conditions in the biogas producing fermenters isoptimised by diverting sterilised or sanitised slurry from the strippertank to the first biogas fermenter, said sterilised or sanitised slurrydo not inhibit or harm the population of biogas producing microbialorganism in the fermenters.
 133. A system according to claim 109,wherein the organic material from which N including ammonia is stripped,is diverted to a biogas reactor in which the conditions is mesophilic.134. A system according to claim 109, wherein the organic material whichis mesophilic fermented, is diverted to a biogas reactor in which theconditions is thermophilic.
 135. A system according to claim 133,wherein the thermophilic reaction conditions include a reactiontemperature ranging from 45° C. to 75° C.
 136. A system according toclaim 133, wherein the thermophilic reaction conditions include areaction temperature ranging from 55° C. to 60° C.
 137. A systemaccording to claim 133, wherein the mesophilic reaction conditionsinclude a reaction temperature ranging from 20° C. to 45° C.
 138. Asystem according to claim 133, wherein the mesophilic reactionconditions include a reaction temperature ranging from 30oC to 35oC.139. A system according to claim 133, wherein the thermophilic reactionis performed for 5-15 days.
 140. A system according to claim 133,wherein the thermophilic reaction is performed for 7-10 days.
 141. Asystem according to claim 133, wherein the mesophilic reaction isperformed for 5-15 days.
 142. A system according to claim 133, whereinthe mesophilic reaction is performed for 7-10 days.
 143. A systemaccording to claim 133, wherein a potential foam formation is limited byadding polymers, and/or plant oils, and/or different salts.
 144. Asystem according to claim 143, wherein the plant oil is rape oil.
 145. Asystem according to claim 143, wherein the salts comprises CaO and/orCa(OH)2.
 146. A system according to claim 109, wherein the organicmaterial is fermented mesophilic and thermophilic each for at least 7days.
 147. A system according to claim 109, wherein part of thefermented organic material from the biogas reactors is reused in thatparticular reactor, said fermented organic material function as aninoculum of the population of microbial organism performing thefermentation.
 148. A system according to claim 109, wherein thefermented organic material comprising a slurry including a liquid withsolid material, is diverted to a first separator, separating the solidmaterials including a limited fraction of the liquid from the main partof the liquid fraction. Said mainly solid fraction comprises organic andinorganic material including P (phosphor) and compounds hereof. Saidmainly solid fraction can be further dried and comprises a fertiliser.149. A system according to claim 109, wherein the first separator is adecanter centrifuge.
 150. A system according to claim 109, wherein thereject water from the first separator is treated in a second separator,said second separator comprising a ceramic micro-filters in which thereject water from the first separator is further processed by aerationand filtration, optionally removing any residues of odour components,any residues of nitrogen compounds and any components containing K(potassium), leaving a clean reject water.
 151. A system according toclaim 109, wherein the reject water from the thermophilic biogas reactoror from the first or second separator is diverted to the land, to awaste water treatment plant or a purifying plant, optionally abiological treatment plant.
 152. The utility of a system or a method ofany of claim 4-151, to eliminate or decline the emission to theenvironment of dust, microbial organisms, ammonia, contaminated air,liquid or any other constitution within the system, especially fromanimal houses.
 153. The utility of a system or a method of any of claim4-151, to improve the utilisation of the energy contained in a biomassincluding organic material.
 154. The utility of a system or a method ofany of claim 4-151, to improve the production of biogas comprisingmethane gas and methane-bearing gas. Said gas may be stored in a tanklocally and/or can be diverted to a commercial net of distributing gas.155. The utility of a system or a method of any of claim 4-151, toobtain separate fractions of N (nitrogen), P (phosphor) and potentiallyK (potassium) from organic materials. Said fractions are of commercialvalue and can be utilised as fertilisers to fertilise agricultural andhorticultural crops.
 156. The utility of a system or a method of any ofclaim 4-151, to obtain an improved animal welfare and improved hygienein animal stables and in accordance to output from said animal stables.Said output comprising manure, slurry and animals to be slaughtered. Theclean animals reduces the risk of infection of meat when the animals areslaughtered.
 157. The utility of a system or a method of any of claim4-151, to abtain a proceedure for rendering animal carcases or fractionshereof, met and bone meal or any other produce from animals availablefor disposing off to agricultural land in the form of refinedfertilizers and thus to benefit from micro- and macro-nutrients in theanimal produce in the agricultural or horticultural plant production.